In a large pot or Dutch oven, melt the butter over medium
Add the onion, season with salt and pepper, and cook until softened but not browned, 5 to 7 minutes. Add carrots, celery, and garlic. Stir a minute until garlic is fragrant
Add the chicken stock, cider, bay leaves and herb stems and bring to a boil over high
Add the noodles and cook, uncovered, over medium-high until the pasta is al dente according to package directions, 7-10 mins
Add the chicken and simmer just until warmed, 1 to 2 minutes. Pluck out the bay leaves and herb stems, stir in the chopped dill, cider vinegar, Dijon mustard, and season to taste with salt and pepper.