1 – To prepare the beer cheese sauce, melt the butter in a medium saucepan over medium-high heat. Add the flour and whisk until smooth. Continue whisking until mixture smells nutty and turns pale brown, about 3 minutes. Reduce heat to medium.

2 – Whisk in milk and beer until smooth. Continue cooking, whisking occasionally, 2 minutes or until mixture has thickened.

3 – Remove from the heat; add cheese and whisk until smooth (the mixture will continue to thicken as it cools.) Whisk in ground mustard, paprika, Worcestershire, and salt to taste. Use immediately or cool to room temperature and store chilled until use.

4 – To prepare burgers, place the ground beef, sausage, salt, onion powder, white pepper, and garlic powder in a bowl; sprinkle with ice water and combine with a fork, stirring just until combined.

5 – Divide the mixture into 4 equal portions; shape each into a 4 ¼ ”inch patty, about ¾” thick.

6 – Prepare grill or heat a large nonstick skillet over medium-high heat. Place burgers on grill or in pan; cook 4 minutes per side or until cooked through. Remove from heat; keep warm.

7 – Heat buns according to package directions and split horizontally. Line the bottom halves of each bun with 1 teaspoon grainy mustard, or more to taste. Top with a lettuce leaf, one burger patty, 1 tablespoon warm beer cheese sauce, and 2 tablespoons french fried onions. Cap with bun tops and serve with remaining beer cheese sauce on the side.