In a large mixing bowl, combine the ricotta cheese, mozzarella cheese, cheddar cheese, Parmesan cheese, chopped spinach, egg, Italian seasoning, onion powder, garlic powder, salt, black pepper, and chopped parsley. Mix thoroughly until fully combined and smooth.
16 oz (454 g) whole milk ricotta cheese, 1 cup (113 g) shredded whole milk mozzarella cheese, 1 cup (113 g) shredded, sharp Cheddar cheese, ½ cup (50 g) shredded Parmesan cheese, 1 cup (140 g) thawed frozen, chopped spinach, 1 large egg, 1 tsp (1 g) Italian seasoning, ½ tsp (1 g) onion powder, ½ tsp (1 g) garlic powder, ½ tsp (3 g) table salt, ½ tsp (1 g) black pepper, ¼ cup (15 g) chopped fresh parsley