In a large bowl, mix together all the ingredients until well combined.
Transfer the mixture into an 11x8 glass baking dish.
Bake in a preheated oven at 400°F for 30 minutes.
Switch the oven to broil and cook for an additional 2-3 minutes to achieve a golden brown top, keeping a close eye to prevent burning.
Allow the dip to sit for 5-10 minutes before serving to let the steam from the spinach settle.
