1poundboneless skinless chicken breasts - cut into bite-sized pieces
1/4teaspoonground black pepper
2cupsbaby spinach - torn into pieces
1/2cupnonfat plain Greek yogurt
1cuppart-skim mozzarella cheese - divided
2tablespoonschopped fresh basil - plus additional for serving
Bake the squash: Preheat the oven to 400 degrees F. Slice the squash in half lengthwise and scoop out the seeds. Drizzle the cut sides with olive oil and sprinkle with salt and pepper. Place the squash cut-side down on a rimmed baking sheet. Drizzle 2 tablespoons water into the baking sheet (this prevents sticking). Bake for 40 to 45 minutes, until the squash flesh is fork-tender and the skin gives a little when pressed. Remove from the oven and set aside to cool. Reduce the oven temperature to 350 degrees F.
Meanwhile, heat a large saucepan over medium and add the bacon. Cook until the bacon is crisp and the fat has rendered, about 8 minutes. With a slotted spoon, remove the bacon to a paper towel–lined plate and pat dry. Discard all but 1 tablespoon bacon fat from the pan and increase the heat to medium high. Add the chicken pieces to the pan and season with garlic powder, salt, and pepper. Sauté until the chicken is cooked through, about 5 minutes. Remove from the heat, then add the spinach. Stir the chicken and spinach together until the spinach wilts, then stir in the Greek yogurt, half of the mozzarella cheese, and basil.
Once the squash is cool enough to handle, use a fork to shred and fluff the inside flesh so it's no longer attached to the walls and makes a "nest." Divide the chicken filling evenly among the boats, using a fork to lightly mix it with the spaghetti squash. Arrange the stuffed squash on a baking sheet and sprinkle with the reserved bacon and remaining mozzarella cheese.
Bake until the cheesy is bubbly, about 10 minutes. Let cool for a few minutes, then serve hot, sprinkled with additional fresh basil.
The squash can be roasted and "shredded" up to 1 day in advance. The entire dish can be assembled up to 1 day in advance as well. Bake as directed just before serving.
Leftovers can be stored in the refrigerator for 4 to 5 days. Reheat in the oven or gently in the microwave. I do not recommend freezing, as the spaghetti squash will become mushy.