Start by trimming the rind off both brie rounds using a small paring knife, then cut the cheese into small pieces so it melts evenly later. Combine it in a bowl with the grated parmesan and alpine cheese. In a separate small bowl, mix the crushed crackers with melted butter until every crumb is coated; this is what gives you that irresistible golden crust later.

Bring a large pot of salted water to a boil and cook your pasta about two minutes short of the package's suggested time. Since the pasta finishes cooking in the oven, undercooking it slightly now keeps it from turning mushy later. Drain it well and set it aside while you make the sauce.

Melt the butter in a medium saucepan over medium heat, then whisk in the flour until fully combined. Keep whisking and cook this mixture for two to three minutes so the flour loses its raw, pasty taste. This step is quick but important, as it sets up the sauce's smooth, velvety base.

Slowly whisk in the milk along with the Dijon mustard and garlic powder, stirring constantly so no lumps form. Keep cooking over medium heat until the mixture visibly thickens, which usually takes about two to three minutes. You want a sauce thick enough to coat the back of a spoon.

Lower the heat and add the cheese mixture one handful at a time, stirring until each addition fully melts before adding more. Going slowly here is what keeps your sauce silky instead of grainy or oily. Taste and season with salt and pepper once all the cheese is incorporated.

Preheat your oven to 375°F and stir the cooked pasta into the cheese sauce until every piece is coated. Pour everything into a greased baking dish and scatter the buttery cracker topping evenly over the top. Bake for 10 to 15 minutes, until the edges are bubbling and the crust turns a deep golden brown, then finish with a sprinkle of parsley before serving.