Caramelized Onion Challah - cooking recipe

Ingredients

10 tablespoons chicken fat
4 cups diced onions
2 1/4 teaspoons instant yeast
3 tablespoons sugar
2 cups warm water, divided
2 tablespoons kosher salt
3 large eggs, room temperature
4 cups unbleached flour
4 cups bread flour
1 large egg, blended with 1 tablespoon water

Preparation

Melt 2 tablespoons chicken fat (schmaltz) in a large nonstick skillet over medium-low heat. Add onions, cover and cook until very soft, about 30 minutes, stirring occasionally. Uncover and cook until brown, about 25 to 30 minutes, stirring frequently. Cool completely.
Melt 8 tablespoons schmaltz and cool to 110\u00b0F.
Place yeast and sugar in bowl of mixer fitted with paddle attachment. Add 1/2 cup water and mix until yeast is dissolved. Gently mix in remaining 1-1/2 cups water, salt and cooled schmaltz. Mix in eggs 1 at a time. Add flour, 1 cup at a time, beating well after each addition and scraping down sides.
Change to dough hook and knead 20 minutes or until very smooth. Turn dough out onto lightly floured work surface; knead 1 to 2 minutes. Place in large oiled bowl, turning to coat. Cover with plastic wrap and set aside in cool place to rise until doubled, about 2 to 2-1/2 hours.
Punch dough down, turn out on lightly floured work surface and knead in onions. Return to bowl, cover with plastic, and let rise 1 hour. Transfer to large plastic bag, leaving room for dough to expand, and refrigerate overnight.
Grease a 12\" springform pan and line with parchment. Heavily flour work surface.
Using floured hands, divide dough into 3 equal-size pieces. Flatten each piece into a rectangle and roll each into a 4-foot long cylinder. Take breaks during rolling so dough can rest. Pinch cylinders together at one end and braid loosely, pinching ends together. Starting at finished end, coil braid into circle, brush end with egg mixture and press into braid. Transfer to prepared pan. Cover with bath towel. Let rise until doubled and very light, about 2 to 2-1/2 hours.
Place baking stone in oven. Preheat oven to 375\u00b0F Brush bread with egg mixture. Place bread in pan on top of baking stone. Bake 20 minutes. Gently remove bread from pan and transfer to the stone. Brush again with egg wash. Bake 50 to 55 more minutes, or until challah is well browned. Cool on wire rack.