How to Make It
Stir together sugar, warm water, yeast, and instant dry milk in bowl of a heavy-duty stand mixer; let sit 3 minutes.
Stir together salt, baking powder, baking soda, and 1 cup of the flour in a separate bowl. Add flour mixture to yeast mixture, and beat on low with dough hook until incorporated. Stop mixer, and add 1 1/2 cups flour. Beat on low until incorporated. Gradually add melted butter, beating until incorporated. Increase speed to medium, and gradually add remaining 1 1/4 cups flour, beating until dough pulls away from sides of bowl.
Transfer dough to a lightly floured surface, and knead until dough is completely smooth and slightly tacky to the touch but not sticky, about 10 minutes. (Knead in more flour, if necessary.)
Place dough in a lightly greased bowl, and cover with plastic wrap. Let rise in a warm place (80°F to 85°F), free from drafts, until doubled in bulk, about 1 hour.
Punch down dough, and shape into 15 (1 1/2-inch) balls. Flatten balls into 3-inch-long logs. Place logs, 1/2 inch apart, on a parchment paper-lined baking sheet. Cover with plastic wrap, and let rise until doubled in bulk, about 1 hour.
Steam buns, in batches, in a covered steamer basket over boiling water until tender, about 12 minutes. Remove basket, and cool, uncovered, 3 minutes. Refrigerate in an airtight container up to 3 days, or freeze up to 2 weeks.
Eventide Oyster Co., Portland, ME