Potato and Vegetable Gratin - Serving Dumplings

Ingredients

• 1.1 pounds starchy potatoes
• 1 pound sweet potatoes
• 1 large zucchini
• 3 large turnips
• 2 tsp salt
• 2 tsp black pepper
• 2 tsp garlic powder
• 2 tsp Italian seasoning
• 1 tsp sweet paprika
• ¼ tsp grated nutmeg
• 3 tbsp olive oil
• 1 cup heavy cream
• 2 ounces grated Parmesan
• 5 ounces grated Gruyère
• ½ tbsp unsalted butter (for greasing)