Wash and dry squash. Cut in half, place face down in ½ inch water in baking dish (I used two 9 x 13 casserole dishes), bake for 25-30 minutes or until fork tender.
While squash in baking saute onions and garlic in olive oil on medium heat until translucent and tender, about 5 minutes.
Add ground chicken and saute until fully cooked, 8-10 minutes. Stir frequently to break up chunks.
Add in tomatoes and saute an additional 1-2 minutes until skin begins to wilt.
Add spinach and saute 1-2 minutes until wilted into mix.
When squash is done baking divide mixture evenly among boats and serve with desired toppings like parmesan cheese, red pepper flakes, etc.