In a small bowl, dissolve yeast with 1 tablespoon sugar in warm water; set aside.
In a separate large bowl, whisk together 6 cups flour, 1/2 cup sugar and salt.
Add beaten eggs and the water with dissolved yeast and sugar to the large bowl of flour.
Stir in oil or melted butter and mix well with a wooden spoon. Once the entire mass sticks together turn out onto a floured surface and knead for about 5 minutes, adding in that last cup of flour as needed to form a smooth, pliable glossy mass. Alternatively, this can be done in a stand mixer with a dough hook. Note: If dough isn't coming together, add more flour, a couple tablespoons at a time, until it pulls away from the bowl. You want the dough to be sticky though.
Oil a large bowl then place dough into bowl flipping it over to make sure it is covered with the oil. Cover with a towel and let dough rise until doubled in bulk.
Punch down, knead one or two times and then divide dough in half.
Divide each half into either 3 strands (or 4 or 6 depending on how intricate your loaf braid will be.) Here is a guide on How to Braid Challah.
Place each braided loaf on a greased large baking sheet (cook spray works well), cover with a dry towel and let rise a second time until loaves are double in size.
Pre-heat oven to 350 degrees. Brush each loaf with a beaten egg, sprinkle poppy seeds or sesame seeds if you wish.
Bake for about 30 minutes or until bread is golden brown on the surface.