1. In a container large enough to hold the brisket, whisk together all the ingredients for the slather.
2. Put brisket in the container with the slather, ensuring all the meat has contact with the slather. Cover the container and allow meat to marinate in the refrigerator for at least six and up to 24 hours. Turn over half-way through to ensure even coating.
3. Place all rub ingredients in mixing bowl and blend 30 sec/speed 10. Set aside. Alternatively, use a food processor or mortar and pestle to blend to a fine powder.
4. When brisket has marinated in slather, remove brisket from liquid and allow it to drain off. Lightly sprinkle rub all over brisket.
5. Allow to sit for another hour, if you can be bothered! If not, proceed with cooking!
6. Preheat oven to 140ºC (280ºF). Place the brisket in a roasting dish, add a splash of beer and cover tightly with foil. Cook for 10 hours. Check occasionally and add a little more beer or water if it’s drying out. See Tips.
Tomatillo Salsa Verde
7. For the salsa, add the onion, garlic and jalapenos to mixing bowl and blend 4 sec/speed 6. Alternatively, use a food processor. Add tomatillos, coriander, lime juice and salt. Blend 15 sec/speed 7 (or in a food processor) to a textured salsa. Add a little water, if necessary, to ensure a wet, spoonable texture.
8. Grill spring onions on a lightly oiled grill until nicely coloured and soft. Lightly toast tortillas in a dry pan. Slice or tear brisket into large pieces. Place some brisket in each tortilla, top with a grilled spring onion and finish with a generous spoon of salsa verde and a few coriander leaves.