Preheat the smoker to 250 degrees F (120 degrees C).
Remove the brisket from the Cryovac packaging. Wipe off excess liquid with paper towels.
Trim the brisket with a sharp boning knife taking care to trim all the fat from both sides of the triangular muscle called the point. This will help create flavorful bark on both sides. The point is used to make brisket burnt ends which are twice cooked points served as little 1-inch (2.5cm) cubes that melt in your mouth.
Remove any silver skin and excess fat from the top of the flat muscle.
Trim off any excess fat cap leaving behind about a 1/2-inch (1.3cm) fat cap. The brisket is cooked fat side-down so you need some fat to protect the brisket from the heat source coming from the bottom of the pit.
Mix the Worcestershire sauce, beef paste, and Maggi Seasoning together. Spread all over the brisket, except for the fat cap. Sprinkle the bonito flakes evenly over the top and let the flakes melt into the brisket.
Apply the rub generously enough to cover the exposed meat so you cannot see it anymore. There is no need to season the fat cap. Sprinkle the rehydrated mushrooms on top.
Put the brisket in the smoker fat side-down. Cook until the crust sets, 5 to 8 hours depending on the pit used.
Spray the brisket with water using a spray bottle once you see bark beginning to form around the edges of the brisket (about 5 hours into the cook). Continue to spray every 30 minutes if you can.
Once you notice that the mushroom bits are cooked and have deposited their umami flavor, remove them to allow the bark under the shitake bits to crust up. Apply rub to reseason any areas that don’t have any.
Continue to cook and remove the brisket from the smoker once the bark has set.
Mix together the beef stock, water, and Maggi Seasoning to form the mop.
Make a double layer of foil twice as long as the brisket. Put the brisket in the foil and make a bathtub shape before you pour in the mopping liquid all over the top of the brisket. Wrap the foil tightly around the brisket taking care to remove all the air pockets. Return to the smoker.
Cook for another 2 to 4 hours until tender. Check for tenderness by using a thermometer tip to probe the brisket from the top and through the foil taking care not to puncture the bottom of the foil pouch. Cook until it feels like the thermometer tip is going through a muffin when the brisket is probed.
Remove and cut open the foil immediately to allow the heat to escape and stop the cooking. It takes me anywhere from 8 to 14 hours to cook a 16-pound (7.25kg) packer in a 250 degrees F (120 degrees C) pit.
Do not put away the brisket to keep warm until the internal temperature drops below 170 degrees F (75 degrees C). On a hot day, this may take 2 hours.
About one hour before you’re ready to serve the brisket, remove the brisket from the foil pouch. Pour the liquid into a fat separator. Discard the foil pouch. Drain off the au jus minus the fat and keep the au jus warm. Remember to taste the au jus and add water if it is too salty.
Place the brisket fat side down on a large cutting board. Use a Grafton edge slicer knife to remove the point from the flat. Trim away any excess fat from the point and then apply some rub onto the sliced areas. Return the flat to the cooler to keep warm and return the point to the 250 degrees F (120 degrees C) pit with the cut side down. Cook for another 45 to 60 minutes to render the fatty point until it looks and feels like the excess fat has been rendered. Remove and spray the point with water to rehydrate it. Cover loosely with foil and keep warm.
In a small bowl, combine the rub, barbecue sauce, and honey.
When ready to serve the flat, trim off excess fat off the cut side of the flat. Apply a thin layer of the finishing sauce mixture on the side where the bark has formed. Slice the brisket flat using a Grafton slicer into pencil-thick slices. Taste and apply some ground-up rub if it’s not salty enough.
Cut the burnt ends point into little 1-inch (2.5cm) cubes. Sauce the point to taste.
Arrange the slices on a nice platter and surround it with the bunt ends.