Cheesy Scalloped Potatoes

A very rich, creamy side dish with loads of potatoes and three cheeses.  My Aunt Lynne introduced me to this recipe and it is wonderful! Pairs well with ham, peas, steak and carrots by Better Homes & Gardens.
Serves 6 - 8

• 1/2 Yellow Onion, chopped
• 1 clove Garlic, minced
• 2 tbsp Unsalted Butter
• 2 tbsp All-Purpose Flour
• 1/4 tsp Black Pepper
• 1/4 tsp Kosher Salt
• 1 1/4 cups Milk
• 3/4 cup Sharp Cheddar, Gruyere and Swiss (mixed evenly), shredded
• 3 Russet Potatoes, thinly and evenly sliced

1. Preheat oven to 350* degrees F. Grease a casserole dish, set aside.
2. In a saucier over high heat, cook onion in butter until onions begin to soften and become translucent. 
3. Add garlic, cook 30 seconds more.
4. Stir in flour, pepper and salt, reduce heat to medium.
5. Add milk and cheese, cook and stir until thick and bubbly.
6. Place half the sliced potatoes in prepared dish, cover with half the sauce.
7. Repeat potato and sauce layer.
8. Bake, covered with foil for 40 minutes.
9. Remove foil and bake 30 minutes or until potatoes and done (top should be slightly golden).