With a sharp knife, slice the squash in half. (If the squash is too tough - puncture in several places forming a dotted line around the squash. Microwave 3-5 minutes to soften. Allow to cool before cutting in half - following the dotted line).
Scoop out the seeds, brush with oil, salt, and pepper, and place face down on a baking tray. Bake for 35-40 minutes or until a fork can easily pierce the skin.
Heat olive oil in a large pan. Add chicken breasts (seasoned with salt and pepper) and garlic, and fully cook.
Add tomatoes and spinach. Cook until spinach has wilted. Add marinara sauce.
Stack the basil leaves and roll them up. Cut into slices and add to pan.
Add crushed red pepper, and stir until the ingredients are fully incorporated.
Once the squash has finished roasting, remove from the oven and let it sit for a few minutes before turning over and pulling at it with a fork. (Careful, there will be some steam!)
Shred the inside of each squash, being careful not to poke through the skin. Pour the sauce over the shredded squash, top with fresh basil, and serve.