Slice your bread . Remove crust. Cut into squares or use cookie cutters to get fun shapes. Spray your skillet with non stick spray (or lightly coat with butter) Toast your breads on ONE side over low -med low heat till buttoms and golden brown.
Cut your mushrooms up relatively small. Mince your onion. Saute in garlic till soft. Add a bit of garlic salt. Blend in your flour and cream. Mix well. Cook several minutes more.
Now pile your mushrooms up in the center of your toasts. Serve right away. Garnish with fresh chopped chives, parsley or watercress sprigs if you like.
My Grandmother always spread a tiny bit of mayo on each toast before adding any topping. I usually spread a bit of cream cheese or butter. All totally optional.