Mushroom and Ricotta Bruschetta

Preheat oven to 425 degrees F (220 degrees C). Mix ricotta, egg, lemon zest, 1/2 teaspoon salt, black pepper, and red pepper flakes in a bowl until smooth. Place toasted bread slices on a baking sheet. Sprinkle with 1 tablespoon olive oil and evenly divide ricotta mixture atop 4 bread slices. Bake in the preheated oven until cheese is browned, about 12 minutes. Heat butter and 1 tablespoon olive oil in a large skillet over medium-high heat; cook and stir mushrooms in mixture until browned, 5 to 6 minutes. Add green onions; cook and stir until softened, 2 to 3 minutes. Stir marsala wine into mixture and cook until reduced by half, about 1 minute. Reduce heat to medium-low. Add chicken stock and lemon juice to skillet; cook until liquid has evaporated. Reduce heat to low. Stir in parsley and butter. Season with salt and black pepper to taste. Spoon mushroom mixture equally atop 4 slices of ricotta-topped bread slices.