Gluten Free Oat Challah

Ingredients

• 2 tablespoons yeast
• 1 tablespoon sugar
• 1/2 cup warm water
• 4 - 4 1/2 cups certified gluten free oat flour (whisk to remove lumps)
• 2/3 cup tapioca flour (starch)
• 1 1/3 cup potato starch
• 1 tablespoon xanthan gum
• 3/4 cup sugar
• 1 teapsoon salt
• 4 large eggs
• 1/2 cup canola oil
• 1 cup seltzer
• 1 large egg
• 1 tablespoon warm water
• sesame seeds, poppy seeds, dried onion (optional)