Diced Potato Casserole with Vegetables

Step 1
Preheat the oven to 350 degrees F (175 degrees C). Grease a large baking dish.

Step 2
Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until potatoes are almost tender, about 15 minutes. Drain in a colander.

Step 3
While potatoes are cooking, melt 2 tablespoons butter in a large skillet over medium-high heat. Cook and stir onion in hot butter until soft and translucent, about 5 minutes. Add zucchini and cook until softened, about 5 minutes. Season with herbes de Provence, salt, and pepper; cook and stir for 1 minute. Add drained potatoes and tomato; cook for 2 minutes.

Step 4
Combine Parmesan cheese and Gruy?re cheese in a bowl. Stir 1/2 of the cheese mixture into potato-vegetable mixture and transfer to the prepared baking dish.

Step 5
Melt remaining 2 tablespoons butter. Stir melted butter into remaining cheese mixture and bread crumbs until combined. Spread evenly on top of potato-vegetable mixture in the baking dish.

Step 6
Bake in the preheated oven until cheese is browned and crusty, 15 to 25 minutes.