Melt the butter over medium-low heat. Add the garlic and cook for about 2–3 minutes until fragrant.
Pour in the heavy cream and milk. Add garlic powder, onion powder, salt and pepper. Gently simmer for 3–5 minutes.
Stir in the Parmesan until melted and the white garlic sauce is smooth and creamy. Remove from heat.
In a large bowl, combine the spinach, ricotta, eggs, mozzarella, Parmesan, onion powder, garlic salt and pepper.
Spread a layer of white garlic sauce in the bottom of your baking dish.
Layer oven-ready noodles, spinach ricotta filling, noodles, white garlic sauce, noodles. Repeat until all your layers are built.
Finish with plenty of white garlic sauce and mozzarella on the top layer!
Cover tightly with foil and bake at 375°F for 45 minutes.
Remove the foil and bake another 15–20 minutes until golden and bubbly. Broil on LOW for a couple minutes at the end if needed for extra color.
Let it rest uncovered for 15–20 minutes before slicing.
