Mix first five ingredients and shape into 3/4" thick patties (about 10). Bake meat patties at 375 for 20 minutes. Transfer to baking dish.
In large skillet, saute onion in a little oil. Add mushrooms when onion starts to cook. Stir in flour to thicken. Add water and beef base and stir over medium high heat until thickened. Pour over meat patties and bake at 350 for 30 minutes. (This can also be done on the stove over low heat. Stir frequently.)
Although spelt is actually a type of wheat flour, most people with wheat allergies can digest spelt with no problem. Obviously, you should not eat spelt if it is a problem for you.
Be careful of the beef broth if you are avoiding wheat or soy. I use Better than Bouillon Organic beef base and, for this recipe, I use two times the amount suggested on the jar for 3 cups of beef broth.
If you don't need gluten-free or wheat-free, go ahead and use all-purpose flour and regular breadcrumbs.
I used a 3 oz. scoop for the meat mixture and ended up with 11 patties plus about a half sized one.