Cook the Sausage: Place a large skillet over medium-high heat. Add the Italian sausage and cook until deeply browned and fully cooked through, breaking it into small crumbles with a wooden spoon as it cooks. Once finished, drain any excess grease and set the sausage aside.

Heat the Beer Base: In a separate large saucepan or Dutch oven, pour in the beer and bring it to a gentle simmer over medium heat.

Melt the Cream Cheese: Cut the softened cream cheese into cubes and add it to the simmering beer. Whisk continuously until the cream cheese is completely melted and the liquid is smooth.

Create the Thickener: In a small bowl, whisk together the milk and flour until no lumps remain. Pour this slurry into the saucepan along with the Dijon mustard, garlic powder, onion powder, salt, and black pepper. Stir well.

Add the Cheeses: Reduce the heat to low. Gradually add the freshly shredded cheddar, mozzarella, and Parmesan cheeses, a handful at a time. Stir constantly until all the cheese is completely melted and the sauce is glossy and thick.

Combine and Serve: Fold the cooked sausage crumbles into the warm cheese mixture until evenly distributed.

Keep Warm: Transfer the dip immediately to a serving dish or a small slow cooker set to "warm." Serve alongside soft pretzels, tortilla chips, or crusty bread.