Preheat your oven to 375°F. Chop your squash in half lengthwise and scoop out the seeds.
Lightly rub the inside of the squash with olive oil to coat, and season with salt and pepper.
Place cut-side down on a foil-lined baking sheet for 45 minutes.
While the squash is baking, melt 2 Tbsp of butter in your skillet. When melted, add the onions and saute until translucent.
Once the onions are starting to soften, add the garlic and cook.
Set the onions and garlic aside, then put the remaining 1 tbsp butter in the pan, then add the chicken. Season to taste and cook until done.
When the squash is done, use a fork to scrape the insides into "noodles," while being careful not to tear or rip the outer shell, as it will be your bowl.
Mix the "noodles" with the chicken, onions, and garlic. Add in the sour cream, breadcrumbs, and 1 cup of cheese, stirring it all together.
Scoop the filling back into the squash shells, add additional seasoning if you prefer, and top with the remaining cheese.
Bake for an additional 15 minutes, then increase heat to broil for 5 minutes to brown the cheese on top. Once it looks good, you're ready to pull it out and serve!