Indulge in a decadent and savory treat with Jim's Beer Mac and Cheese Gratin

Ingredients

• 8 oz elbow macaroni
• 3 tbsp unsalted butter
• 3 tbsp all-purpose flour
• 1 cup beer (such as an amber ale or lager)
• 2 cups milk
• 2 cups sharp cheddar cheese, shredded
• 1 cup Gruyere cheese, shredded
• 1/2 tsp mustard powder
• Salt and pepper, to taste
• 1 cup panko breadcrumbs
• 2 tbsp parsley, chopped