Preheat oven to 375 Degrees,
Add all ingredients to a blender, except for the Spinach. Blend till desired texture is reached. Add more milk as needed to reach desired texture. Could also use an immersion blender.
Next, add in the spinach and stir until evenly mixed throughout.
Put all ingredients into a shallow, oven proof, ungreased baking dish and bake for 30-40 minutes, until the top has slightly browned.