Heat up the oil in a large pan.
Add the ribs, season them with salt and pepper, and sear on both sides.
Remove them from the pan and add them to the slow cooker.
In the same pan, add the peeled and chopped onion and garlic, and fry them on a low heat until golden.
Add the tomato paste, Worcestershire sauce, seasoning and stock, and mix well.
Pour the mixture over the ribs and cook everything on high for 4 ½ hours or on low for 8-9 hours.
Strain the liquid in which the ribs cooked.
In a small bowl, mix the cornflour with 2 tablespoons of water and mix well to get a slurry.
Add the slurry to the strained liquid and pour everything in a pan set over a medium heat.
Simmer for 2-3 minutes until it thickens into gravy.
The meat should be tender enough to just pick up the bones that are falling apart.
Serve them with mashed potatoes and gravy.