Cheese sauce: In a small saucepan over medium heat, melt butter and stir in flour until smooth. Cook 1-2 minutes, stirring constantly. Slowly stir in the milk, cream, minced garlic, dried onions, and season with salt and pepper. Whisk sauce on low until smooth and slightly thickened. Reduce heat and stir in 2 cups of shredded cheese until melted and smooth. Taste sauce and add additional salt, pepper, garlic or onion flakes, if desired.

Prep Potatoes: Peel the potatoes if you'd like. Slice the potatoes into very thin 1/8'' slices.

Layer: Place half of the sliced potatoes in a lightly greased 9x13 inch casserole dish. Pour half of the cheese sauce over potatoes. Layer the remaining potatoes on top. Spoon the remaining cheese sauce over the potatoes. Sprinkle remaining cheese on top.

Bake: Cover with aluminum foil and bake at 350 degrees F for 30 minutes. Remove foil and continue baking, uncovered, for an additional 30 minutes, or until potatoes are cooked, cheese is browned, and sauce is bubbly.