Season the beef burgers patties with salt and pepper. Use your thumb to press an indent into the center of each patty, to keep the burgers from bulging when they cook.
Cook the burgers on a preheated grill on medium high heat for 5-6 minutes, until seared. Flip the burgers and cook them for another 4-5 minutes for medium rare, or a bit longer if you want them to be well done.
Add a slice of pepper jack cheese to each burger, and cook for another 2 minutes, or until the chese melted.
Toast the brioche buns, if desired.
Place a burger on the bottom half of your toasted bun. Top each slider with a few slices of avocado, pickled red onion, and a drizzle of the chipotle mayo.