Potatoes and Onions and Cheese, Oh My!

This is the recipe my husband uses when he makes Potatoes Au Gratin. You will need to refer to Peter's Cheese Sauce for this to make the cheese sauce. Using a food processor or mandoline to slice the veggies is key.

• Ready In: 1 hr 50 mins
• Serves: 4-6

Ingredients

• 2  tablespoons butter
• 4 -6  potatoes (depending on size)
• 2  onions
• 2  cups whole mushrooms
• 2  tomatoes, sliced (optional)
•  salt and pepper, to taste

• Cheese Sauce

• 2  tablespoons butter
• 2  tablespoons flour
• 200  g cheddar cheese, grated
• 400  ml milk
• 50  g cheddar cheese, grated (See Peter's Cheese Sauce for preparation of sauce)

Directions

1. Preheat oven to 200C/400°F.
2. Generously butter the inside of a 9X13 baking dish and set aside.
3. Peel the potatoes and thinly slice along with the onions and mushrooms, using a food processor or mandoline.
4. Layer half the potatoes into the bottom of the baking dish, then half of the onions, followed by half the mushrooms. Season with salt and pepper. Repeat layers with remaining veggies and season with salt and pepper.
5. Pour cheese sauce over potatoes and cover with aluminum foil.
6. Bake for 1 1/4 hours. Remove from oven and take foil off. Put a single layer of sliced tomatoes on top, if using. Sprinkle with remaining 50g cheese and return to oven for 15 minutes, turning on broiler/grill for the last 3-5 minutes to brown cheese.
7. Allow to sit 10 minutes before serving.