The Pizza Parlour Potato Bake Cheesy Casserole Recipe

Ingredients

• 5 lbs Russet or Yukon Gold Potatoes, peeled and quartered
• 4 tbsp Unsalted Butter
• 1/2 cup Whole Milk or Half-and-Half, warmed
• 1/4 cup Grated Parmesan Cheese
• 1 large Egg Yolk
• 1 tsp Kosher Salt
• 1/2 tsp Black Pepper
• 1/2 tsp Garlic Powder
• 1 tbsp Olive Oil
• 1 lb Italian Sausage, casing removed
• 1/2 medium Yellow Onion, finely diced
• 1/2 cup Sliced Mushrooms
• 1/2 cup Sliced Black Olives (pitted)
• 1 tsp Dried Oregano
• 1/2 tsp Dried Basil
• Pinch of Red Pepper Flakes (optional)
• 1 cup Marinara Sauce
• 5 cups Shredded Low-Moisture Mozzarella Cheese
• 1/4 cup Fresh Basil leaves, chiffonaded