In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Heat a large skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes; drain excess fat. Transfer bacon to a paper towel-lined plate.
Melt butter in the skillet. Add garlic, and cook, stirring frequently, until fragrant, about 1-2 minutes. Whisk in flour until lightly browned, about 1 minute. Gradually whisk in milk. Cook, whisking constantly, until incorporated, about 1-2 minutes.
Stir in butternut squash, sage and Dijon. Bring to a simmer, stirring occasionally, until slightly thickened, about 5 minutes. Stir in Parmesan and heavy cream until incorporated; season with salt and pepper, to taste.
Stir in pasta and chicken, and gently toss to combine.
Serve immediately, garnished with bacon and sage, if desired.