Stir in the peas until heated through. Add salt and pepper to taste.
To serve, mound the mashed potatoes in the center of a platter and ladle the chicken mixture over it. Season generously with additional salt and pepper.
For a thicker broth, make a paste by whisking 1/2 cup flour into 1/2 cup cold water in a small bowl until smooth. Pour a little of the paste into the pot after the noodles are cooked. Stir until well-blended and boil for 1 minute, adding more thickening as desired.