Preheat oven to 400° F.
Place bread on a baking sheet. Combine butter, garlic and paprika, and spread on one side of each slice of bread. Combine cheeses, and sprinkle evenly over butter.
Bake until bread is crisp and cheese is bubbly, 10-15 minutes.
Find it online: https://afoodieaffair.com/french-onion-salisbury-steak/