Prep and roast the squash: Preheat oven to 400°F (200°C). Carefully halve the spaghetti squash lengthwise and scoop out the seeds. Rub the cut sides with a little olive oil, season with salt and pepper, and place cut-side down on a parchment-lined baking sheet. Roast 35–45 minutes, until the strands pull apart easily with a fork and are tender but not mushy.

Crisp the bacon: While the squash roasts, cook bacon in a large skillet over medium heat until crisp. Transfer to a paper towel–lined plate. Crumble once cooled. Pour off most of the bacon fat, leaving about 1 teaspoon in the pan for flavor.

Cook the chicken: Season chicken all over with salt, pepper, and half the Italian seasoning. Add 1 tablespoon olive oil to the same skillet over medium-high heat. Cook chicken 4–6 minutes per side, until browned and cooked through (165°F/74°C internal temp). Rest 5 minutes, then slice or cube.

Start the sauce base: In the same skillet over medium heat, add butter (if using). Stir in minced garlic and cook 30–60 seconds until fragrant. Pour in chicken broth, scraping up browned bits. Reduce heat to medium-low and simmer 2 minutes.

Make it creamy: Whisk in milk and remaining Italian seasoning. Sprinkle in Parmesan a little at a time, whisking until melted and smooth. Remove from heat and whisk in Greek yogurt until creamy. Season with salt, pepper, and crushed red pepper to taste.

Shred the squash: When squash is cool enough to handle, use a fork to rake the flesh into spaghetti-like strands. Place strands in a large bowl and pat with paper towels if very wet.

Toss it all together: Add squash strands, chicken, and most of the bacon to the skillet with the sauce. Toss gently over low heat until everything is coated and warmed through. If the sauce seems thick, add a splash of broth or milk. If too thin, stir in more Parmesan.

Finish and serve: Taste and adjust seasoning. A small squeeze of lemon brightens the sauce nicely. Top with remaining bacon, extra Parmesan, and chopped parsley. Serve hot.