Preheat oven to 375°.
Drain and chop artichoke hearts.
Thaw and squeeze out spinach. Chop if it is not prechopped.
Finely mince the garlic and dice the onion.
In a pan, heat the olive oil and cook the onions until translucent.
Add in the garlic and cook lightly.
Toss in the spinach and artichokes and cook until any remaining liquid is gone. Wait until some of the artichoke pieces have very lightly browned.
Transfer the above mixture to a large bowl and add in the salt, pepper, and crushed red pepper.
Mix in the cream cheese, parmesan, ricotta, and ⅓ of the mozzarella.
Transfer to an oven safe dish, about 8 inches wide, and top with the remaining ⅓ mozzarella.
Bake for 22 - 25 minutes, until the mozzarella has melted and browned a bit.