Sago is a familiar star in the world of Chinese dessert soups (tong sui), often simmered with other ingredients to create light and refreshing sweet treats.
Think classics like Sweet Potato Sago Dessert Soup, Mung Bean Soup with Sago, or Red Bean Soup with Sago.
But today’s recipe takes sago in a fresh new direction.
This Purple Sweet Potato Sago Cake doesn’t follow the soup route.
Instead, it transforms sago into a delicate, translucent wrapper, encasing a vibrant purple sweet potato filling.
Using a mooncake mold gives them a beautiful, intricate shape.
The result? A dessert that’s visually stunning and has a subtly sweet, satisfying taste—absolutely perfect for an afternoon tea snack.
Pro Tip for Success
When you steam the purple sweet potato, you might find some water has collected in the bowl.
It‘s crucial to pour off all this excess liquid before mashing. If the filling is too wet, it can prevent the sago wrapper from holding its shape, leading to cakes that might fall apart or crack.
Ingredients and Substitutions
For the Sago Wrapper:
- Sago Pearls – I recommend using small, white sago pearls (sometimes labeled tapioca pearls). Look for ones that are uniform in size for even soaking and cooking. The quality matters here—good sago will swell and become beautifully translucent, not gummy.
- Hot Water – The temperature is crucial. Water around 60-70°C (140-158°F) is the perfect balance. It’s hot enough to start dissolving the sago starch and soften the pearls quickly, but not so boiling that it causes them to clump together into a sticky mess.
- For the Filling:
- Purple Sweet Potato – This is the star for color and flavor. Its natural sweetness and vibrant hue are perfect. Look for firm potatoes with deep purple flesh. Orange sweet potato or pumpkin can be used for a different color and flavor, though the sweetness level may vary.
- Condensed Milk – A small amount adds a lovely creamy, caramelized sweetness and helps bind the mashed potato. If you don’t have it, you can substitute with an equal weight of granulated sugar, though the flavor will be less rich.
For Handling:
- Cornstarch – This is our non-stick helper. A light dusting on the shaped cakes prevents them from sticking to your hands, the mold, and each other during the final steaming stage.
How to Make Steamed Sago and Purple Sweet Potato Cakes
Soak the Sago Pearls
Place the sago pearls in a large, heatproof bowl. Bring water to a boil and let it cool for a minute, or use a thermometer to reach 60-70°C (140-158°F).
Pour the hot water over the sago pearls.
Stir immediately with a spoon or chopsticks to ensure all pearls are submerged and not clumping.
Cover the bowl and let it soak for 30 minutes. Do not stir during this time. The sago will absorb the water and become a thick, gelatinous, semi-translucent mass with a slightly grainy texture.
Prepare the Filling
While the sago soaks, prepare the purple sweet potato. Peel and slice it into 1cm thick rounds for faster steaming.
Place the slices in a steamer basket. Steam over boiling water for 15-20 minutes, or until extremely tender and easily pierced with a fork.
Transfer the steamed sweet potato to a bowl. While still hot, add the condensed milk (or sugar). Use a potato masher, fork, or the back of a spoon to mash it into a completely smooth, lump-free paste. Let it cool to room temperature.
Shape the Filling and Dough
Once the sweet potato mash is cool, divide it into 12 equal portions(about 20g each if using 250g potato). Roll each portion between your palms into a smooth, round ball. Set aside on a plate.
After 30 minutes, the sago will be ready. It should look like a sticky, cohesive dough.
Gently knead the sago mixture in the bowl for just 30 seconds to make it more uniform.
Divide the sago dough into 12 equal portions (about 30-33g each). Roll each portion into a ball. Keep your hands lightly wet to prevent sticking.
Assemble the Cakes
Take one sago ball. Flatten it in the palm of your hand into a disc about 3-4 inches wide.
Cup the disc in your hand to form a small “bowl.”
Place one sweet potato ball in the center.
Gently bring the edges of the sago wrapper up and around the filling.
Pinch the top to seal completely, then gently roll between your palms to form a smooth ball again.
If using a mold: Press the ball into a lightly dusted mooncake or dim sum mold. Press firmly, then unmold onto a piece of parchment paper.
Steam the Cakes
Prepare your steamer. Line the steamer basket with parchment paper or cabbage leaves, and cut small holes for steam.
Arrange the shaped cakes in the steamer, leaving about 1 inch of space between them as they will expand slightly.
Add cold water to the steamer pot. Place the basket in the pot.
Turn the heat to high. Once the water reaches a full, rolling boil and steam is pouring out, start timing. Steam on high heat for 25 minutes.
Do not open the lid during steaming.
Cool and Serve
After 25 minutes, turn off the heat. You can remove the cakes immediately.
The cakes will be very soft and sticky when hot. Let them cool on the parchment for at least 15-20 minutes. As they cool, the sago wrapper will firm up slightly and become beautifully translucent, revealing the purple filling inside.
Serve at room temperature for the best texture. They can be enjoyed slightly warm or cold.
Tips & Tricks
- Use the correct water temperature for soaking sago – 60–70°C ensures the pearls soften evenly without clumping or staying hard in the center.
- Handle soaked sago gently – knead lightly to avoid breaking the pearls, which can affect texture and appearance.
- Let the purple sweet potato cool before shaping – this prevents burns and reduces stickiness.
- Stick to the 30g sago : 20g filling ratio – this keeps the outer layer thick enough to wrap without tearing.
- Steam from cold water – gradual heating prevents cracking and ensures a smooth, chewy finish.
- Steam long enough – the full 25 minutes is important for the sago to fully cook and become pleasantly bouncy.
Frequently Asked Questions
My sago dough is still very grainy and has white hard centers after soaking.
This means the water was not hot enough, or the soaking time was insufficient. Ensure your water is between 60-70°C. If it’s still grainy after the full 30 minutes, you can try gently kneading it for another minute; the friction sometimes helps. If hard centers persist, the sago may be of lower quality.
The cakes are very sticky and impossible to handle after steaming.
This is normal when they are piping hot. You must let them cool on the parchment paper. As they cool, the starch sets and they become much less sticky and easier to pick up. Dusting with cornstarch before steaming is also crucial.
Can I use other fillings?
Absolutely! Red bean paste, lotus seed paste, or even a sweetened coconut and peanut filling are all delicious alternatives. Just ensure your filling is not too wet, and is cooled and shaped into firm balls.
How do I store leftovers?
Store cooled cakes in an airtight container in the refrigerator for up to 3 days. The sago wrapper will harden when cold. To serve, re-steam them for 5-7 minutes until soft and warm again. They do not freeze well, as the texture of the sago becomes unpleasantly hard and changes upon thawing.
Crystal-Clear Steamed Sago Cake with Purple Sweet Potato Filling
Ingredients
For the Sago Wrapper
- 200 g small white sago pearls
- 200 g hot water 60-70°C / 140-158°F
For the Purple Sweet Potato Filling
- 250 g purple sweet potato peeled weight, sliced
- 15 g sweetened condensed milk or 15 g granulated sugar
For Assembly
- Cornstarch for dusting
Instructions
Soak the Sago Pearls
- Place the sago pearls in a large, heatproof bowl. Bring water to a boil and let it cool for a minute, or use a thermometer to reach 60-70°C (140-158°F).
- Pour the hot water over the sago pearls.
- Stir immediately with a spoon or chopsticks to ensure all pearls are submerged and not clumping.
- Cover the bowl and let it soak for 30 minutes. Do not stir during this time. The sago will absorb the water and become a thick, gelatinous, semi-translucent mass with a slightly grainy texture.
Prepare the Filling
- While the sago soaks, prepare the purple sweet potato. Peel and slice it into 1cm thick rounds for faster steaming.
- Place the slices in a steamer basket. Steam over boiling water for 15-20 minutes, or until extremely tender and easily pierced with a fork.
- Transfer the steamed sweet potato to a bowl. While still hot, add the condensed milk (or sugar). Use a potato masher, fork, or the back of a spoon to mash it into a completely smooth, lump-free paste. Let it cool to room temperature.
Shape the Filling and Dough
- Once the sweet potato mash is cool, divide it into 12 equal portions(about 20g each if using 250g potato). Roll each portion between your palms into a smooth, round ball. Set aside on a plate.
- After 30 minutes, the sago will be ready. It should look like a sticky, cohesive dough.
- Gently knead the sago mixture in the bowl for just 30 seconds to make it more uniform.
- Divide the sago dough into 12 equal portions (about 30-33g each). Roll each portion into a ball. Keep your hands lightly wet to prevent sticking.
Assemble the Cakes
- Take one sago ball. Flatten it in the palm of your hand into a disc about 3-4 inches wide.
- Cup the disc in your hand to form a small "bowl."
- Place one sweet potato ball in the center.
- Gently bring the edges of the sago wrapper up and around the filling.
- Pinch the top to seal completely, then gently roll between your palms to form a smooth ball again.
- If using a mold: Press the ball into a lightly dusted mooncake or dim sum mold. Press firmly, then unmold onto a piece of parchment paper.
Steam the Cakes
- Prepare your steamer. Line the steamer basket with parchment paper or cabbage leaves, and cut small holes for steam.
- Arrange the shaped cakes in the steamer, leaving about 1 inch of space between them as they will expand slightly.
- Add cold water to the steamer pot. Place the basket in the pot.
- Turn the heat to high. Once the water reaches a full, rolling boil and steam is pouring out, start timing. Steam on high heat for 25 minutes.
- Do not open the lid during steaming.
Cool and Serve
- After 25 minutes, turn off the heat. You can remove the cakes immediately.
- The cakes will be very soft and sticky when hot. Let them cool on the parchment for at least 15-20 minutes. As they cool, the sago wrapper will firm up slightly and become beautifully translucent, revealing the purple filling inside.
- Serve at room temperature for the best texture. They can be enjoyed slightly warm or cold.
Leave a Reply