Wash the spinach thoroughly and remove the roots and any yellow leaves.

Bring a pot of water to a boil, then blanch the spinach briefly. Transfer the blanched spinach to a blender.

Add water at a 1:1 ratio of spinach to water, then blend until completely smooth.

If there are any visible particles, blend again until the purée is very fine. Measure out 170 g of spinach purée for the dough.

In a medium bowl, combine the 170g of warm spinach puree with the baking soda, yeast, and sugar. Stir well until everything is dissolved.

In a large mixing bowl, add the 300g of flour. Pour the spinach-yeast mixture into the flour.

Using a spatula or your hands, mix until a shaggy dough forms. Turn it out onto a clean, lightly floured surface.

Knead the dough vigorously for 10-15 minutes. Use the heel of your hand to push the dough away, then fold it back over itself. Continue until the dough is very smooth, elastic, and no longer sticky. Form into a ball, place in a lightly oiled bowl, cover, and set aside.

Warm the water to about 30–40°C — warm to the touch but not hot. Add the yeast and sugar, stirring until dissolved.

Place the flour into another large bowl. Slowly pour in the yeast mixture while stirring until a shaggy dough forms.

Knead the dough into a rough ball, then knead on the work surface for about 10–15 minutes until smooth, elastic, and evenly textured.

Roll the spinach dough and white dough separately into rectangular sheets, about 3–5 mm thick.

Place the white dough sheet directly on top of the spinach dough sheet, aligning the edges.

Fold the stacked dough toward the center, and fold it over once more to one side, then divide it into three equal portions.

Roll each portion thin, then stack all three sheets together.

Cut the stacked dough into strips about 2 cm wide.

Turn the strips upright so the cut sides face up, and arrange them tightly together. At this point, you'll clearly see the marble pattern forming.

Roll the dough into a thin sheet once more.

Starting from one end, roll it up tightly into a log — this creates a spiral marble pattern inside the buns.

Gently roll the log into a long cylinder, then cut into small, evenly sized pieces.

Place the shaped buns into a steamer, leaving space between each one to allow for expansion.

Cover and let the buns proof in a warm, slightly humid environment for 30–60 minutes, until noticeably puffed and almost doubled in size. When lightly pressed, the dough should slowly spring back.

Bring a pot of water to a boil. Steam the buns over high heat for 12 minutes. Turn off the heat and let the buns rest in the steamer for another 3 minutes before opening the lid.