• Remove corned beef brisket from the packaging (toss the seasoning packet), and soak the brisket in water for at least 4 hours, changing the water at least once during the soaking process. Remove from the water and pat it dry.

Cook on the Traeger:

• Set the Traeger temperature to 275℉ and preheat with the lid closed for 15 minutes.
• Place the brisket directly on the grill grates, fat-side up. Close the lid and cook for 2 hours.
• In a small bowl, add the mustards, brown sugar, paprika, onion powder, and pepper; stir until combined. Set aside about 2 Tbsp of the sauce (to add at the very end of cooking).
• Double line 2 large pieces of foil (enough to completely wrap the brisket with extra). Add ½ of the sauce in the middle of the foil, and then with tongs, transfer the hot brisket to the foil, fat-side up. Pour the remaining sauce mixture over the top of the brisket, using a spatula to spread it evenly. Bring the foil up and over the brisket to completely seal the package tightly.
• Return the brisket to the grill, re-insert the probe, and continue to cook until the internal temperature reaches 203°F, 2 hours more.
• Remove the cooked brisket from the grill; carefully open the foil, but cover it loosely with a piece of foil and let rest for 15 to 20 minutes before slicing.
• Slice the meat about ¼” thick, cutting it against the grain, and serve with a mustard sauce. Also serve with your favorite side dishes like potatoes, carrots, or cabbage.

Make the mustard sauce:

• In a small bowl add the sour cream, mustard, and sugar. Mix until combined. Keep in the fridge until ready to serve.

Cook in the oven:

• Preheat the oven to 350 degrees.
• In a small bowl, add the mustards, brown sugar, paprika, onion powder, and pepper; stir until combined. Set aside about 2 Tbsp of the sauce (to add at the very end of cooking).
• Double line 2 large pieces of foil (enough to completely wrap the brisket with extra). Add 1/2 of the sauce in the middle of the foil, and then with tongs, transfer the hot brisket to the foil, fat-side up. Pour the remaining sauce mixture over the top of the brisket, using a spatula to spread it evenly. Bring the foil up and over the brisket to completely seal the package tightly.
• Place in the oven; bake for 50 minutes per pound (so about 4 hours). Or, better yet, check the internal temperature with a quick-read thermometer to see that it has reached 145 °F.
• Remove from the oven and carefully open the foil; spread the rest of the mustard mix that you reserved on the top. Turn the oven up to 375 degrees and bake for 15 more minutes (uncovered).
• Remove from the oven and cover it loosely with a piece of foil and let rest for 15 to 20 minutes before slicing.
• Slice the meat about 1/4” thick, cutting it against the grain, and serve with a mustard sauce. Also serve with your favorite side dishes like potatoes, carrots, or cabbage.