Step 1

Combine the starter with the water and 2 cups of the flour in the bowl of a stand mixer or a large mixing bowl. Mix to form a thick batter. Cover the bowl and set aside for 30-60 minutes.

Step 2

Add the sugar and salt. Switch to the dough hook. Add the remaining flour and mix to combine. The dough should eventually cling to the hook and start to clear the sides of the bowl. If the dough is still a little sticky sprinkle in a little more flour, just a tablespoon at a time.

Step 3

Knead 5 minutes on medium speed. If working by hand, stir in as much of the flour as you can, then turn the dough out onto a lightly floured surface and knead in the remaining flour. Knead 5 minutes. Form the dough into a smooth ball.

Step 4

Put the dough into a lightly oiled bowl, turning once to coat the dough. Cover the bowl and set it aside at room temperature.

Step 5

After 30 minutes uncover the bowl, lift one side of the dough and fold it into the middle of the dough. Repeat with the other three sides of the dough then flip the dough over. You're basically turning the dough inside-out to redistribute the yeast. Cover the bowl and after 30 minutes repeat the procedure. Cover the bowl and after 60 minutes repeat the procedure again. Cover the bowl and after 60 minutes the dough should be ready to shape (total fermentation time is about 3 hours. By now the dough should be lively, elastic and airy. If the dough is still sluggish give it another hour or two at room temperature.

Step 6

Meanwhile, make the filling.

Step 7

Melt the butter in a sauté pan. Add the minced onion and salt and sauté until the onions are soft and translucent, but not browned.

Step 8

Remove from the heat and add the poppy seeds. Add salt and pepper to taste. Set aside to cool. Refrigerate until ready to use.

Step 9

Generously flour a parchment-lined baking sheet. Turn the dough out onto a lightly floured surface without kneading. Divide the dough into 10 equal portions. Roll each portion to a ball.

Step 10

Pick up a piece of dough. Pinch the dough and gently pull to form a 4" disc. Set each bialy onto the prepared baking sheet, leaving 2" between for room to rise. Cover the pan with plastic wrap and place the pan in the refrigerator overnight.

Step 11

In the morning, take the pan out of the refrigerator. Generously sprinkle two baking sheets with corn meal. (see note)

Step 12

Working carefully not to deflate the dough, pick up a bialy and gently re-stretch to about 4" around. Use your fingers to form a depression in the middle of each bialy. Set each bialy onto the prepared baking sheet, leaving 2" between them. Place 5 bialys onto each pan,

Step 13

Cover the pan loosely with plastic wrap and set aside to rise for about 1 hour. The bialys will not double in size, but they should be noticeably lighter and increase about 50%. Meanwhile, preheat the oven to 450°F.

Step 14

Spoon a teaspoon of filling into the middle of each bialy and gently push to reform the dimple in the middle. Bake until lightly browned, about 20 minutes.

Step 15

Serve slightly warm or room temperature.