Preheat the oven to 400℉.
In a large pot, melt the butter over low heat. Remove two tablespoons and set aside in a medium bowl.
Add the milk and lager to the pot and bring to a steady simmer. Season to taste with salt and pepper. Add the macaroni and cook, stirring regularly, until the macaroni is mostly cooked through and creamy, around 10-12 minutes.
Add in the cheddar, mozzarella, and fontina. Continue cooking until the cheese is completely melted and very creamy, another 3-4 minutes.
Remove the pot from heat and transfer the macaroni mixture to a medium casserole dish.
To the reserved butter, add the garlic, breadcrumbs, and parmesan; mix well. Spread the breadcrumb mixture on top of the macaroni.
Place in the oven to bake until golden brown and crispy on top, approximately 15-20 minutes. Allow to cool for 10-15 minutes before serving. Enjoy!