Season pork with salt and pepper and dust with flour. In a medium, deep skillet, melt the butter in the olive oil. Add the pork and cook over high heat, turning once, until lightly browned, about 3 minutes. Transfer pork to a plate.
Add the onion to the skillet. Cover and cook over moderate heat, stirring occasionally, until softened, about 10 minutes. Stir in the mustard and 1 teaspoons of flour and cook for 1 minute. Add the chicken broth and bring to a boil.
Nestle the pork in the onion sauce. Cover and simmer over moderate heat until the pork is cooked through, about 8 minutes. Transfer pork to plates. Stir the chopped dill into the sauce and spoon over the pork. Serve with buttered noodles.