Preheat the oven to 350 degrees F.
In a medium saucepan, heat the butter over medium high heat.
Once the butter starts sizzling, add garlic and onions and saute until they are soft and translucent.
Add in the beef and saute until the meat browns slightly.
Pour in the sauce, stir and heat until it starts bubbling.
Add in the sliced olives and turn down the heat to medium low.
Let the sauce simmer for 5 minutes. then remove from heat.
Using a sharp knife or a mandolin, cut out thin slices of kabocha squash, about 1/8 inch thick.
In a 9x13 baking dish, spoon and spread out a little bit of the meat sauce.
Lay the kabocha slices in a single layer.
Sprinkle with cheese if using.
Spread 1/3 of the meat sauce.
Repeat steps 10-12 two more times.
Top off with some more cheese if using.
Bake in the preheated oven for 1 hour and 10 minutes.
Take it out, let it cool a bit before serving!