Stir together mustard and honey in a small bowl and set aside. Meanwhile, bring a large pot of salted water to a boil. Cook pasta until tender with a bite, about 9 minutes, or according to package instructions. Reserve 1/2 cup pasta water, drain, and set aside.

While pasta cooks, heat a large deep skillet over medium heat. Add bacon and cook until crisp, about 5 minutes. Remove bacon from skillet to a paper towel-lined plate and reserve drippings in the skillet.

Add chicken to the hot skillet; cook until browned on all sides (chicken will not be fully cooked through at this point). Remove chicken from skillet and keep warm. Add light green parts of the onions to skillet and cook until tender, 1 to 2 minutes. Stir in honey mustard and heavy cream.

Return chicken to skillet and add salt and pepper. Bring to a simmer and cook, stirring occasionally, until slightly thickened and chicken is no longer pink at the center. Add pasta and reserved pasta water to skillet and cook until heated through.