Rye Walnut Rolls

Directions

1. 1
   Line 2 large baking sheets with parchment paper. 3Cook onion with 1/4 teaspoon salt in oil in a 10-inch skillet over medium heat, stirring occasionally, until softened, 4 to 5 minutes. Drain onions in a sieve set over a bowl, reserving onions. Stir milk into onion oil in bowl.
2. 2
   Stir together yeast, warm water, and honey in a large bowl and let stand until foamy, about 5 minutes. (If mixture doesn't foam, start over with new yeast.)
3. 3
   Mix flours, pepper, milk mixture, and remaining 2 3/4 teaspoons salt into yeast mixture with a wooden spoon or rubber spatula until a soft dough forms. Turn out dough onto a floured surface and knead, dusting surface and your hands with just enough flour to keep dough from sticking, until dough is elastic and smooth, about 6 minutes.
4. 4
   Pat dough into a 9-inch square and sprinkle with onions and walnuts. Fold dough over to enclose filling and pinch edges to seal. Knead to distribute onion and nuts throughout dough, dusting with just enough flour to keep dough from sticking, about 2 minutes. (Dough will be lumpy; if any nuts or pieces of onion pop out, just push them back in.)
5. 5
   Put dough in an oiled large bowl and turn to coat. Cover bowl with plastic wrap and a kitchen towel and let dough rise in a draft- free place at warm room temperature until doubled, 1 1/2 to 2 hours.
6. 6
   Punch down dough (do not knead), then halve. Roll half of dough on a lightly floured surface with lightly floured hands into a 12-inch-long log (keep remaining half covered with plastic wrap). Cut log into 12 equal pieces and roll each into a ball by cupping your hand and pushing dough against work surface as you roll in a circular motion. Arrange rolls 2 inches apart on a baking sheet. Cover rolls with a kitchen towel (not terry cloth). Make more rolls with remaining dough, arranging and covering them on second sheet. Let dough rise in a draft-free place at warm room temperature until doubled, 1 to 1 1/2 hours.
7. 7
   Preheat oven to 375°F with racks in upper and lower thirds.
8. 8
   Brush rolls with egg wash and sprinkle with nigella seeds. Bake, switching position of sheets halfway through, until golden brown, 20 to 25 minutes. Transfer rolls to a rack and cool at least 20 minutes.