Pour the oil, salt and sugar into a large mixing bowl. Add 1 cup of boiling water and stir; add 1/2 cup of cold water. Dissolve 2 packages of dry yeast in 1/3 cup of warm water. Beat 3 eggs, add oil and water mixture, saving about 1-2 tablespoons for the brushing of the loaves before baking. Add dissolved yeast and stir. Add seven cups of unbleached flour and mix well. Turn out onto a floured board and knead the dough until it does not stick to your hands. Add more flour (a bit at a time) if needed. Return the dough to the bowl and cover with a clean towel. Place in the oven that has been preheated for one minute and then turned off. Let the dough rise for one hour. Turn the dough out onto a floured board and knead for about one minute. 

Learn how to braid challah

Place on baking sheet after braiding and let rise for 45 minutes at room temperature. Brush top with egg mixture and sprinkle with sesame or poppy seeds. Bake for 40 minutes at 375° F. Remove loaves and let cool on a wire rack.