Drop 1 1/2 sticks of unsalted butter in a small microwave-proof bowl. Add 1 tsp of black pepper and 8 pressed cloves of garlic. Microwave for 1 minute or until the butter melts. Remove the bowl from the microwave and let the butter infuse with garlic and pepper for 5 minutes. Strain the butter into the bowl with the beef broth, add the beer, salt, and whisk well.
Next, inject the mixture into the brisket. Stir well each time before refilling the injector. You may want to cover the meat with a large sheet of plastic to prevent splattering. When done, cover with foil or plastic and refrigerate overnight.
The next day, remove the brisket from the pan and pat dry with paper towels. Give it a light coating of salt, pepper, and granulated garlic and onion all over. Pat with your hand to help the seasonings stick. The amount of rub is up to you. If you like your brisket more peppery, add more pepper.
Transfer the meat to the preheated smoker. Do not throw out the marinade or wash the marinade pan, keep it refrigerated.
Smoke the brisket at 200F - 225F for 10-12 hours. Transfer the meat back to the pan and cover loosely with foil. Let the brisket cool down to room temperature, cover tightly and refrigerate again.
The following day, preheat the oven to 250F and cook the brisket cover with foil for 4 hours.
Remove from the oven, loosen the foil and let rest for 10-15 minutes. Transfer to a cutting board, slice and serve with your favorite side dishes.