2tablespoonschopped fresh basilplus additional for serving
Place a rack in the center of your oven and preheat the oven to 400 degrees F. Roast the spaghetti squash according to this recipe for Roasted Spaghetti Squash. 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, 1/4 teaspoon salt, and 1/4 teaspoon 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.
MAKE-AHEAD: 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.
TO STORE: Leftovers can be stored in the refrigerator for 4 to 5 days.
TO REHEAT: Warm in the oven or gently in the microwave.
TO FREEZE: I do not recommend freezing, as the spaghetti squash will become mushy.