Preheat oven to 400 F and line a baking sheet with parchment paper. Cut your squash in half, and place cut side down on a rimmed baking sheet. Bake in preheated oven for 30-40 minutes, until your squash shreds easily with a fork.
Use a spoon to remove and discard the seeds. Allow your squash to cool before shredding, then shred and set aside.
Meanwhile, sprinkle both sides of the chicken with 1/2 teaspoon of both salt and pepper. Heat a pan over medium-high heat, and melt the butter and 1 tablespoon of oil. Once the pan is hot, sear the chicken on 1 side. Once the first side is golden brown, flip and reduce the heat to low. Place a lid on top and continue to cook until the internal temp of your chicken reaches 165 F. Set cooked chicken aside on a plate and tent with foil.
Increase the heat of your pan to medium and add the remaining tablespoon of oil. Cook the garlic for 1 minute, then add the heavy cream, chicken broth, Italian seasoning, salt, and parmesan cheese, and stir. Continue to cook until the sauce is warm and the cheese melts.
Remove from heat and stir in the spinach and sun dried tomatoes. Once the spinach has wilted, add the spaghetti squash and toss to coat in the sauce. Taste and adjust to your liking, you may want to tweak the salt depending on the size of your squash.
Slice chicken and stir in or serve on top. Option to scoop back into the squash shells. Sprinkle with additional parmesan and fresh parsley. Enjoy!