Making the Spinach water:

1. Puree 3 cups of firmly-packed spinach leaves with ¾ cup warm water. Strain the puree through a sieve.
2. Use the spinach water in the dough and discard the pulp, or make quick bread with the pulp. After straining, you should have about 160 g of warm spinach water.

Making the dough:

1. Place the flours, sugar, yeast, baking powder, and salt in the bowl of a stand mixer. Stir or whisk to combine.
2. Pour in the warm spinach water, and using the dough hook, mix on low speed to form a shaggy dough.
3. Increase the speed to medium-high and mix about 5-6 minutes more until the dough is smooth and slightly tacky.
4. Form the dough into a smooth ball and place in a large bowl. Cover with plastic wrap, bees wrap, or a kitchen towel, and proof in a warm spot until doubled in size, about 1 to 1 ½ hours. Optionally, place in the refrigerator to proof for at least 6 hours or overnight.
5. Once the dough has doubled in size, deflate it and place it on a lightly floured work surface. Then, shape the dough into a smooth ball.

Shaping the Buns:

1. Cut 12 4-inch squares of parchment paper. The parchment squares are used to create a non-stick surface so the steamed buns don’t stick to the steamer.
2. Using a bench scraper, or sharp knife, divide the dough into 12 equal pieces. A scale works really well for this part, if you have one. The total dough weight is about 528 grams so each piece will be about 44 grams.
3. Fashion each piece into a smooth ball, and place on a parchment square. Cover the buns with a damp towel or lightly greased plastic wrap. Let the buns rise until they are about 1 ½ times their size, about 30-45 minutes.

Steaming the Buns:

1. A double-stacked bamboo steamer with a lid works well for steaming these buns. However, you can steam the buns in any set up you prefer, including a double boiler steamer set up, a steamer basket (working in batches), or a frying pan with the bamboo steamer set up.
2. Start by adding water to a wok, or a pot that fits the size of the steamer, bring it to boil, and then turn it down to simmer.
3. Meanwhile, arrange the buns, (on the parchment squares) about 2” apart in the steamer. You should be able to fit 3 buns on each level. (Cover the remaining 6 buns with greased plastic and place in the refrigerator to keep them from over proofing while the other buns are steaming.)
4. Set the bamboo steamer (with the buns), in the wok to steam for 10 minutes. Turn the heat off and let the buns rest for 5 minutes in the steamer to keep them from collapsing. (You’ll be tempted to remove the lid and look at the buns, but don’t do it! Let them rest.)
5. After 5 minutes, remove the buns and let them cool slightly before serving.
6. Repeat with the remaining 6 buns.
7. Slice and enjoy with your favorite sandwich fixings.