Preheat oven to 350° Fahrenheit. Generously butter 2 qt. baking dish or small cast iron skillet.
In a large measuring cup, whisk together mayonnaise, broth, lemon juice, salt, pepper & garlic. Set aside.
Slice both squashes in approximately 1/4 inch slices for crisp tender baking. Place in a large mixing bowl. Pour mayo/broth mixture over squash and toss until well coated. Arrange (or just spoon) coated squash in buttered baking dish. Pour any leftover sauce over top of squash.
Using a fork, mix together panko, Parmesan and Italian seasoning in a small bowl to make topping. Sprinkle evenly over the top of the squash (you may or may not use it all). Cover with foil and bake in preheated oven for 30 minutes.
Remove foil. Change oven setting to broil. Brown topping for 5-7 minutes. Remove from oven and serve.