1. In a medium skillet over medium-low heat, melt 1½ tablespoons butter. Add garlic and breadcrumbs, and cook while stirring frequently until breadcrumbs are lightly toasted and fragrant. Remove from heat, season with salt and pepper, and stir in parsley. Set aside.

2. Boil elbow macaroni in well-salted water until just al dente. Reserve 1 cup of the pasta water before draining. Set aside.

3. In a large saucepan over medium heat, melt 2 tablespoons butter. Sprinkle in flour and whisk together for 1 minute.

4. While whisking, slowly pour in the Guinness, milk, half and half, salt, pepper, and Dijon mustard. Bring to a simmer, whisking frequently until the mixture thickens slightly.

5. Add cream cheese and 2½ cups shredded cheddar to the sauce. Stir until completely smooth.

6. Add the drained macaroni to the sauce and stir to combine.

7. Add the remaining 1 cup shredded cheddar and stir until melted for extra cheesy texture.

8. Let the mac and cheese sit over low heat for a few minutes, stirring frequently, so the pasta absorbs more of the sauce.

9. If the sauce thickens too much, stir in a bit of the reserved pasta water or more milk to loosen it up.

10. Transfer to a serving bowl or individual bowls and sprinkle with the toasted breadcrumb topping.

11. Serve immediately.