Challah

Whisk yeast, 2 tsp. sugar, and ¼ cup warm water in the bowl of a stand mixer (or a large bowl if kneading by hand). Let sit until foamy, about 10 minutes.

Whisk eggs, salt, ½ cup shortening, ¾ cup sugar, and 2 cups warm water in a medium bowl. Add egg mixture and 7 cups flour to yeast mixture. Beat with dough hook on medium speed until dough is smooth, elastic, and very sticky and pulls away from sides of bowl, about 10 minutes. (Alternatively, knead dough on a lightly floured surface until smooth and elastic, about 10 minutes.)

Grease a large bowl with shortening; transfer dough to bowl. Cover with plastic wrap and let sit in a warm place until doubled in size, 1½–2 hours.

Turn out dough onto a lightly floured surface and divide into 6 equal portions. Shape each into a 17"-long rope.

Grease 2 rimmed baking sheets with shortening. Place 3 ropes side by side on each prepared sheet. Working with one at a time, pinch logs together at 1 end; braid, then pinch ends together and tuck under. Let sit in a warm place until 1½ times larger, about 1 hour.

Preheat oven to 325°. Beat egg yolks and 2 Tbsp. water in a small bowl. Working with one at a time, brush dough with egg wash and sprinkle with sesame seeds. Bake first loaf 15 minutes, then increase oven temperature to 425° and continue baking until browned and sounds hollow when tapped, 15–20 minutes more. Let cool on baking sheet.

Reduce oven temperature to 325°, then leave oven door open 5 seconds to cool down. Repeat baking with remaining dough.

Do Ahead: Challah can be made 3 days ahead; keep tightly wrapped at room temperature, or freeze up to 1 month. Let cool before storing.