We recommend using a standard potato peeler to peel the raw squash, but if you want to save some time, you can buy packaged raw butternut squash cubes in the grocer's product section—equal to three cups of cubes.
Use a pastry brush or napkin to coat a 9x13 casserole dish with olive oil. Set aside.
In a small bowl, combine topping ingredients. Set aside.
In a deep skillet, heat butter and add the squash, onions and garlic. Cover and stir occasionally until squash is starting to get tender but not soft, about 15 minutes.
Add milk, cream, and seasonings. Add more salt and pepper to taste.
Reduce heat to low and simmer uncovered until you see the liquid is cooking away and getting a little thicker, about 10 to 15 min.
Gently blend with a potato masher if any large chunks remain.
Carefully transfer the hot mixture from the skillet to the oiled casserole dish.
Sprinkle all of the topping on the casserole.
Bake uncovered 400F for 25 to 30 minutes or until the top is golden.
Let set for five minutes then serve warm.