ИСТОЧНИК - Foodienarium -
This is the recipe that I've tried from the latest Jamie Oliver's cookbook.

Serves: 6 plus leftovers Servings
Cook: 15 mins

Ingredients

1,5 - 2 kg beef (brisket or rib-eye)
olive oil
2 large onions
2 tsp mustard
1 bunch fresh rosemary (or other herbs like oregano, thyme)
salt and pepper

Instructions
Preheat the oven to 170C (325F). Place a large casserole pan on a high heat.
Season your piece of beef with salt and pepper and brown it in the hot pan with a lug of olive oil. In the same time peel and slice the onions.
Turn the heat off and place the onions underneath your piece of beef.
Spread the mustard over the meat and strip over most of the rosemary leaves or other fresh herbs.
Protect the meat with a wet piece of greaseproof paper, then tightly cover the pan with a lid or with a double layer of tin foil.
If you're cooking the brisket then cook for around 5 hours for carvable meat, or around 5 for pulled meat. If you're cooking a rib-eye - 3-4 hours is more than enough.
Don't forget to check the meat halfway and add a splash of water if needed.