Preparation

• Position a rack in the center of the oven and heat the oven to 400°F. Grease a 9×13-inch baking dish with butter.
• Cook the bacon in a large (12-inch) skillet over medium heat, stirring frequently, until very crisp, 15 to 20 minutes. Use a slotted spoon to transfer to paper towels. Discard or save the bacon fat for another use.
• Meanwhile, bring a large pot of salted water to a boil, and cook the pasta according to package directions untilal dente. Drain and set aside.
• 在用来煮意大利面的同一锅中，融化4汤匙。用中火的黄油。撒上面粉并煮熟，搅拌，直到变成2至3分钟的淡金色糊。不断搅拌，慢慢加入蒸发的牛奶。搅拌直至光滑，然后在啤酒中搅拌。继续烹饪，搅拌和刮擦锅底，直到酱汁煮熟并稍微变稠，3至5分钟。
• Remove from the heat, and stir in both cheeses a handful at a time. Stir in the ground mustard and 1/2 tsp. salt. If the sauce seems too thick, add a splash of beer to thin it out. Stir in the pasta and bacon, and season to taste with salt.
• Transfer the pasta to the prepared baking dish. Melt the remaining 4 Tbs. butter in a small saucepan over medium-low heat or a medium bowl in the microwave. Stir in the panko and a pinch of salt. Scatter evenly over the pasta.
• Bake until the edges are bubbly and the crumbs are golden, 15 to 20 minutes. Let cool for 10 to 15 minutes before serving.