Add pasta, chicken base, 1/3 cup water, mustard, cream cheese, shredded cheese, 1/4 tsp. pepper, and a pinch of salt to hot pan. Stir to combine. Bring to a simmer.Once simmering, stir occasionally until sauce is slightly thickened and pasta is heated through, 1-2 minutes.If sauce is too thick, add additional water, 1-2 Tbsp. at a time, until desired consistency is reached.Remove from burner.