Combine the stout, garlic, tomato paste, Worcestershire, and horseradish in the slow cooker. Whisk to combine.

Add a tablespoon of canola oil to a skillet. Heat over high heat for a minute or two until the oil starts to ripple. Season the short ribs liberally with salt and pepper. Sear each side for a minute until dark golden. Remove from heat and transfer to slow cooker.

Cook short ribs for 12-16 hours on low. Keep short ribs on warm setting until ready to add to the mac and cheese.

Bring a large heavily salted pot of water to a boil. Add noodles and cook according to packaging instructions. Cook until al dente and then drain.

Add butter back to the pot you just finished using for the noodles. It saves on dishes. Heat the butter over medium/low until it melts. Whisk in the flour until a roux forms. Cook the roux for two minutes.

Add the garlic and whisk to combine. Heat for an additional minute.

Reduce the heat to low. Pour in the milk. Add the salt, cumin, and paprika. Whisk to combine.

While stirring, slowly increase the heat to medium. Keep whisking until the sauce thickens. Add in the cheese and reduce heat to low.

Once the cheese melts, add the noodles. Mix to combine. Add more salt and black pepper if needed. Remove pot from heat and cover with lid until short ribs are prepared.

Now, prepare the short ribs. Remove the bones and toss in the garbage. Add the short ribs to a small plate. You should be able to use the side of a fork to gently push and pull the meat apart.

Pour the sauce through a mesh strainer lined with a paper towel into a large measuring cup or bowl.

To serve, add some mach and cheese to a bowl. Top with a big pile of shredded short ribs, and few spoonfuls of reserved cooking liquid, and a sprinkle of freshly chopped parsley.