Season oxtail with all marinade ingredients.
Marinate for at least 2 hours (overnight is best). If you can, let it sit for 24–48 hours for even deeper flavor.
Heat oil in a heavy pot over medium-high heat. Sear oxtail until deeply browned on all sides.
Add beef broth, remaining marinade and ketchup to the pot, starting with about ¼ cup and adjusting based on color and flavor. Stir well, then simmer until the oxtail is tender. Cover and simmer for 2–2.5 hours until tender.
Remove meat from bones and reduce the gravy until thick and glossy. Stir in butter beans if using.
Boil pasta in salted water until just al dente. Drain and set aside.
Melt butter in a saucepan. Whisk in flour and cook for 1–2 minutes.
Slowly whisk in heavy cream until smooth. Add seasonings and cook until thickened. Reduce heat and stir in cheeses until melted and creamy.
In a bowl, mix panko, parmesan, butter, olive oil, and seasonings until crumbly.
Preheat oven to 375°F.
In a baking dish or ramekins: Add oxtail with a little gravy on the bottom. Spoon mac and cheese on top. Add extra cheddar (optional)
Sprinkle parmesan crumble
Bake for 20–25 minutes until bubbly and golden.
Optional: broil 1–2 minutes for a crisp top.