In a small bowl mix yeast with the warm water and sugar and proof about 5-10 minutes until really foamy. Add honey to the (foamy) yeast mixture and stir. Set aside.
Mix the flours in a large bowl with the salt and xanthan gum.
In a small container mix 4 whole eggs plus 2 egg yolks with the oil.
Add the yeast mixture and the egg mixture to the large bowl with the flour. In a hand held mixer, mix on low until the flour is incorporated into the wet ingredients. Increase speed to medium-high and mix for an additional 2 minutes. Scrape down sides, mix another minute. The batter will be very sticky at this point.
Scrape the dough/batter into the center and place a greased (use spray or oil) parchment paper directly on the dough to cover during the first rise. Let the batter rise in a warm spot for about two hours or until doubled in size.
Punch down and mix again on medium speed for another two minutes.
Place dough in a well sprayed or oiled 9 inch round cake pan or tube cake pan. Mix 1 egg with a splash of water and brush on the dough liberally. Let dough rise uncovered until doubled in size.
Preheat oven to 375 F. Brush dough gently with left over egg wash and cover with your choice of seeds.
Bake 30 minutes until bread sounds hollow and top is golden brown. The internal temperature should be about 200 F.
Remove bread from the pan - place on a rack and cool completely.
NOTE: Make sure to cool the challah on a rack completely before wrapping and storing the bread or it will end up soggy. You can refresh the bread by heating it in a 300 F oven for about 5 minutes before serving.
GLUTEN FREE FLOUR: 1.25 cups superfine brown rice flour, .75 cup superfine white rice flour, 1.5 cups tapioca flour