Melt the butter in a heavy 8-inch skillet or a 1 quart saucepan over low-heat. Add the feta and ricotta cheese, and pepper. Cook, stirring constantly, and mashing the cheeses slightly, until they soften and begin to bubble - about 5 minutes.
Stir in lemon juice, and garnish with the parsley if desired. Serve at once; as the fondue cools, it loses flavor.
Substitute Fontina cheese for the Feta Cheese or you can substitute cottage cheese for the ricotta. You can make both of these substitutions.