Cook bacon in a Dutch oven over medium-high heat until crisp. Remove bacon from pan, reserving 2 teaspoons drippings in pan. Crumble bacon; set aside. Add leek, salt, and pepper to pan; sauté 3 minutes or until tender. Add bacon, mussels, and cider; bring to a boil. Cover and cook 5 minutes or until mussels open; discard any unopened shells.
Place about 9 mussels into each of 4 shallow bowls. Ladle about 1/2 cup broth mixture into each bowl, and sprinkle each serving with 1 1/2 teaspoons chopped parsley.
Beer note: When creating this meal, don't forget to chill the beer. Porter is a versatile style of dark beer that is less charred-tasting and lighter-bodied than most stouts. Try Sierra Nevada Porter ($8/six-pack) from California. Medium-bodied with grapefruit hop notes, it's light enough for a spinach salad, with caramel, coffee, and smoky flavors to complement the bacon and mussel broth. -Jeffery Lindenmuth