Mix mustard, paprika, black pepper, and garlic together in a bowl. Remove roast from wrapping paper and pat dry with a paper towel. Sprinkle dry rub evenly over roast on all sides, rubbing in with your fingers. Let sit on a plate at least 30 minutes to come to room temperature while you prep the vegetables. (Never cook cold meat.) If making on a work day, after coating the beef with dry rub, place in a covered dish in the refrigerator until morning.

In a small saucepan, bring to a boil the stock, wine, vinegar, salt, and bay leaves. Turn down just to a simmer and keep hot. (If making in advance, just mix together the night before. You don't have to preheat this either if you are pressed for time in the morning.)

Bring meat to room temperature. Put the fat or oil in a heavy pan and melt over medium heat. When it shimmers, add the beef, browning about three minutes per side. (Skip this step on busy mornings and just put it straight into the slow cooker with the stock mixture.)

Place stock mixture into a large slow cooker on Low. Add beef. Cover and cook for 8-10 hours.

When meat is done, remove to a cutting board. It will be fall-apart tender at this stage.

Strain pan juice into a small saucepan using a fat-separating cup or skimming off most of the fat first.

Put 1/4 cup of the juice into a small bowl with cornstarch, tapioca flour, or arrowroot powder and whisk to make a smooth slurry.

Put the pan on medium heat and bring to a boil.

Whisk in the slurry, cooking the gravy until it thickens. Serve at once.

Peel all the vegetables and cut into uniformly sized pieces, on the smaller side. Slice the cabbage into wedges, removing the core. If using green onions, just use the white parts, reserving the green leaves for making stock another day.

Toss vegetables with the oil or fat until evenly coated. Sprinkle with black pepper and a small amount of sea salt (if using).

Spread vegetables in a roasting pan and cover with heavy foil. (If making ahead, place in refrigerator.)

40 minutes before dinner, preheat oven to 450F/230C/gas mark 7. Remove pan from refrigerator and make sure it's close to room temperature before putting in oven so you don't crack it.

Roast for 30 minutes until veggies are nearly tender when pierced with a fork, then remove foil and roast another 10 minutes until vegetables are crispy outside and tender inside.

Serve with gravy and meat.