Step 1: Prepare the Potatoes & Sausage

1. Preheat oven to 375°F (190°C).
2. Heat butter and olive oil in a skillet over medium heat.
3. Add sliced smoked sausage and cook for 4-5 minutes, stirring occasionally, until browned.
4. Remove sausage and set aside. In the same skillet, add onions and garlic, cooking for 2-3 minutes until fragrant.
5. In a large bowl, toss diced potatoes with paprika, salt, pepper, and parsley.

Step 2: Make the Cheese Sauce

1. In a saucepan, melt butter over medium heat.
2. Stir in flour and cook for 1 minute, whisking constantly.
3. Slowly add milk and heavy cream, whisking to prevent lumps.
4. Add garlic powder, onion powder, and ground mustard.
5. Stir in shredded cheddar and mozzarella cheese, whisking until smooth. Remove from heat.

Step 3: Assemble the Casserole

1. In a greased 9×13-inch baking dish, spread half of the potatoes.
2. Add half of the browned sausage, then pour half of the cheese sauce over it.
3. Repeat the layers with the remaining potatoes, sausage, and cheese sauce.
4. Top with extra shredded cheddar cheese.

Step 4: Bake to Perfection

1. Cover with foil and bake for 40 minutes.
2. Remove the foil and bake uncovered for an additional 15 minutes, or until the potatoes are tender and the top is golden and bubbly.
3. Sprinkle with fresh parsley for garnish.

Step 5: Serve & Enjoy!

1. Let the casserole cool for 5 minutes before serving.
2. Serve warm with a side of green salad, roasted vegetables, or crusty bread.
3. Enjoy this cheesy, creamy, and utterly comforting meal!