Turn on the oven to preheat to 180 degrees. In a small bowl, combine both types of cheese, chopped mushrooms, spinach, egg, oregano, salt, and black pepper.
Place salami slices one at a time on the bottom of small muffin dishes. Fill 3/4 of the molds with cheese filling.
Place the molds on a baking sheet and in a preheated oven. Bake the appetizer for 20-25 minutes. Remove the finished muffins from the oven, allow to cool slightly, and then gently run a knife along the edge of the mold, remove the snack muffins from the molds and serve immediately.