3 tablespoons extra virgin olive oil
2 tablespoons butter
8 heaping cups chopped yellow squash
1 large onion, chopped
1 cup shredded Parmesan cheese
1/2 cup mayonnaise
Kosher salt and coarsely ground black pepper to taste
1 cup Italian style panko bread crumbs
3 tablespoons melted butter
Preheat the oven to 350 degrees. Spray 9 x 9 inch casserole dish with nonstick cooking spray.
Heat the oil and 2 tablespoons butter in a large skillet over medium heat. Add the squash and onion, and cook until squash is crisp-tender. Transfer to a large bowl and stir in the Parmesan and mayonnaise. Add salt and pepper to taste. Pour into casserole dish. Stir together the panko crumbs and 3 tablespoons melted butter and sprinkle on the squash. Bake for 20 minutes or until the top is golden brown and bubbly.