Mac and Cheese with Chips and Beer

Name: Mac and Cheese with Chips and Beer
Prep time: 15 min
Cook time: 40 min
Yield: 6
Ingredients: 3 tbsp (45 ml) butter; 1 small onion, diced; 1/4 cup (60 ml) all-purpose flour; 1 (330 ml) bottle beer (lager or ale); 1 cup (250 ml) milk; 2 tsp (10 ml) mustard ground (club house); 1/2 tsp (2 ml) sea salt grinder (club house); 1 pinch pepper ground cayenne (club house); 2 1/2 cups (625 ml) shredded old Cheddar cheese; 2 cups (500 ml) elbow macaroni; 1 cup (250 ml) lightly crushed plain or salted potato chips (about 60 g)