Lightly grease a 9x13” and preheat the oven to 400 degrees F.
In a large pot of boiling, salted water, cook potatoes for about 5 minutes until nearly cooked through (they should still have a bite to them). Drain and set aside.
Meanwhile, start cooking your sauce. In a medium pot, melt butter. Add garlic and cook 1 minute. Whisk in flour and cook 1 minute. Stir in milk slowly with a whisk until combined. Cook, stirring frequently, over medium heat until thickened. Add salt to taste. Assemble your dish.
Spread half of the potatoes in the bottom of your dish. Top with half of your white sauce, half of the pizza sauce, half of the pepperoni, and half of the cheese (*see note). Repeat layers with the remaining ingredients.
Bake for 20-30 minutes until hot and bubbly. Let rest 5 minutes before serving.
Notes
*Note: I layered my 2 sauces, but you can easily stir them together