To make gluten free “fried” onions, preheat oven to 475 degrees. Lightly grease a baking sheet and set aside. Combine onion slices, ⅓ cup flour blend and salt in a large bowl, tossing until onions are evenly coated. Pour out onto prepared baking sheet, separating onion rings. Bake in preheated oven for 15 to 20 minutes until golden brown, tossing one or two times. Remove from oven and set aside while you prepare the casserole.
To make the casserole, turn oven temperature down to 400 degrees.
If using fresh beans, boil them in lightly salted water for 5 minutes. Rinse with cold water and drain. If using canned beans, rinse, drain and set aside.
In a large saucepan, melt the butter. Toss in sliced mushrooms and pepper and stir over medium heat for 5 minutes.
Add spices and gluten free flour, stirring to coat. Cook an additional minute and add sour cream and soup. Reduce heat to medium-low and cook while mixture thickens, about 5 to 8 minutes more.
Remove from heat and stir in half the “fried” onions and the drained beans.
Pour mixture into a large casserole dish and cook in preheated oven for 10 minutes or until bubbly. Sprinkle remaining prepared onions on top and bake an additional 5 minutes. Serve warm.
TIP: Pressed for time? Top the gluten free casserole with gluten-free Funyuns Onion-Flavored Rings