Heat large saucepan over medium heat. Add chopped bacon and cook 4 to 6 min., or until edges turn crispy. Stir in celery, onion and potato. Cook until softened, 3 to 4 min. If bottom of pot is browning too much, add 1 tbsp (15 mL) water at a time, as needed.
Slowly pour in beer and bring mixture to a boil over high heat. Reduce heat to low; simmer uncovered 5 min., until potatoes are tender and liquid has reduced by about half. Add mussels, cover and cook until shells open, about 4 min. Discard any unopened mussels. Stir in parsley. Serve with crusty bread.
Substitute an equal amount of small clams for mussels.