• Peel the onions and cut them into a 2cm (¾) dice.
• Cut the celery and carrot into a 2cm (¾") long pieces.
• Peel the garlic cloves and bash them with the side of a knife.
• Cut the tomato into a 2cm (¾") dice.
• Season the oxtail with salt and pepper, then dredge it with flour, tapping off any excess..
  
• Heat a 24cm dutch oven over a medium-high heat and when it is hot add the oil. If you are cooking this in a slow cooker, you can use a 28cm or 11" skillet or frying pan. Sear the beef on all sides, then remove and set aside. You should do this in two batches.
  
• Add the onions, celery and carrot to the pan you cooked the oxtail in and cook for 10 minutes, it should soften and begin to colour.
  
• Throw in the garlic and tomato and cook for another 2 minutes.
  
• Crush the juniper berries with the side of a knife and add them to the pot with the bay leaf.
  

To Cook on a Hob/Stovetop:

• Return the oxtail to the pan and pour over the red wine, sherry and beef stock.

  Add a lid and cook for 3-4 hours over a very low heat. The meat is cooked when it is almost falling away from the bone.
  

To Cook in the oven:

• Return the oxtail to the pan and pour over the red wine, sherry and beef stock.
• Add a lid, transfer to the oven, and cook for 3-4 hours at 150° or 300°F. The meat is cooked when it is almost falling away from the bone.

To Cook in a slow cooker:

• Transfer the vegetables to the base of the slow cooker and add the oxtail.
• Pour over the red wine, sherry and beef stock and add a lid, cook on low for 6-7 hours or on high for 3-4 hours. The meat is cooked when it is almost falling away from the bone.

To Finish the Dish:

• Carefully remove the meat and set it aside. You can also get rid of the bay leaves now.

  Blend the sauce in either a blender or with a stick blender (optional), then return it to the cooking pan.
  
• Return the oxtail and gently heat through for a final 10-15 minutes.