Step 1

Grate 8 ounces sharp cheddar cheese (about 2 cups) and 4 ounces Gruyère cheese (about 1 cup) on the largest holes of a box grater.

Step 2

Melt 3 tablespoons unsalted butter in a medium saucepan over medium heat. Add 3 tablespoons all-purpose flour, 1/2 teaspoon garlic powder, and 1/2 teaspoon onion powder, and whisk until the flour is completely absorbed, about 30 seconds. The mixture will be foamy and there should be no dry pockets of flour left.

Step 3

While whisking constantly, slowly pour in 1 (12-ounce) beer and 1 cup whole milk. Bring to a simmer over medium heat, whisking often, 2 to 3 minutes. Continue to cook, whisking often, until thickened enough to coat the back of a spoon, about 5 minutes.

Step 4

Reduce the heat to low. Add 1/2 teaspoon kosher salt and the grated cheese a handful at a time, whisking between each addition, until the cheese is fully melted before adding more. Serve immediately.