Most Amazing Challah

Sprinkle yeast over water in a large bowl and stir gently to moisten yeast. Stir in salt, sugar, margarine, and 4 eggs; beat well. Gradually mix in flour, 1 cup at a time, up to 12 cups, until dough becomes slightly tacky but not wet. Turn dough out onto a floured surface; knead until smooth and elastic, 8 to 10 minutes.

Grease baking sheets, or line them with parchment paper and set aside.

Cut dough into four equal-sized pieces (or 2 pieces to make 2 large loaves). Cut each piece into thirds for 3-strand braided loaves. Working on a floured surface, roll small dough pieces into ropes about the thickness of your thumb and about 12 inches long. Ropes should be fatter in the middle and thinner at the ends. Pinch 3 ropes together at the top and braid them. Starting with the strand to the right, move it to the left over the middle strand (that strand becomes the new middle strand.) Take the strand farthest to the left, and move it over the new middle strand. Continue braiding, alternating sides each time, until loaf is braided; pinch ends together and fold them underneath for a neat look. Repeat for remaining loaves.

Place loaves onto the prepared baking sheets; let rise until double in size, 1 to 1 1/2 hours.

Preheat the oven to 350 degrees F (175 degrees C). Whisk 1 egg with vanilla extract in a small bowl; brush loaves with egg wash. Sprinkle each loaf with about 1 tablespoon of sesame seeds.

Bake in the preheated oven until tops are shiny and golden brown, about 30 minutes. Let cool before slicing.