Blend Sirloin chuck, brisket, and short rib ground beef mixes. I suggest you prepare this a day before grilling. Patty into 8-oz patties and refrigerate for 24 hours before using; this will help the patties stay together and not fall apart as you grill them.

Make sure the grill is scorching before putting the patties on it. Season the patties with salt and pepper and add a little oil. Roll the sides of the patties so they are fully seasoned.

Make sure the burgers are at room temperature for 10 minutes before grilling them. Look for the hottest part on the grill and place the burger patties down on it. The secret is to move the patties as little as possible once you place them on the grill.

Begin preparing the hamburger buns while the burgers are cooking. Season the buns with salt and pepper and crisp them on both sides on the grill.

Season the thick-sliced onions with salt and pepper, add some oil and place onions on the grill as the buns and burgers cook.

Start basting your patties by brushing them on each side for about two minutes before taking them off the grill to add more flavor. Grill each burger patties for 3 1/2 to 4 minutes on both sides.

Thirty seconds before the patties come off the grill, you need to season the patties again, then add your jack cheese on top to melt while the burgers are still on the grill.

Set up the Brioche buns; add the mustard mayo blend, lettuce, and tomatoes before taking the burger patties off the grill. First, place a tablespoon of mustard mayo blend on both sides of the top and bottom of the bun. Then, gently fold the lettuce to fit onto the bun and press down on the lettuce, ensuring it stays folded.

After the mustard mayo blend and lettuce, add a thick slice of tomato to the lettuce, season the tomato with salt and pepper, and dab more mayo on top.

Add the burgers to each of the pre-made dressed Brioche buns. Place grilled onions on top of each patty. Finish by placing the top bun.