Preheat the oven to 375°F (190°C) and lightly spray the cups of a muffin pan with non-stick spray. In a large bowl, combine cream cheese, feta cheese, parmesan cheese, egg, spinach, dill, garlic, and black pepper. Stir well to combine.
Bake in the preheated oven for about 20 minutes, or until puffed and golden brown. Remove from the oven, allow to cool in the pan for 10 minutes, then with a knife loosen the edges and remove the puffs onto a wire rack to cool completely.