2 tablespoons butter
1 leek, including 1-inch of green, cleaned and finely diced
1 Granny Smith apple, peeled and finely diced
2 tablespoons Calvados
1 tablespoon cider vinegar
3 cups chicken broth
1 cup authentic apple cider
12 ounces boneless, skinless chicken breast
2 cups fine egg noodles (dry)
1/2 cup heavy cream
1/4 cup grated Gruyere (optional)
Salt and freshly ground black pepper
Snipped chives, for garnish

Heat butter in a saucepan. Add leeks and Granny Smith apple, cover and simmer until tender, for about 5 minutes. Add the Calvados and reduce until almost evaporated. Stir in the cider vinegar, broth, apple cider and bring to a simmer.
Add the chicken and egg noodles to the broth, cover and cook until the chicken is cooked through, about 5 minutes. Skim off any fat which is floating to the surface, stir in the heavy cream, optional Gruyere and season, to taste, with salt and pepper. Garnish with chives.