Preheat a griddle with one side set to high heat and the other to medium-low. Place a small pot on the medium-low side and warm the canned chili, stirring occasionally.
Divide the ground beef into 4-ounce balls. Place each ball on the hot side of the griddle. Using a burger smasher with a piece of parchment paper between the meat and the smasher, press firmly until flattened, creating crisp, lacy edges.
Lightly season each patty with the chili seasoning and Montreal steak seasoning.
Add the butter to the griddle, swirling it around the patties to help crisp the edges.
In a bowl, prepare the slaw by mixing the broccoli slaw, chipotle aioli, apple cider vinegar, and BBQ sauce. Set aside.
After a few minutes, or once the beef is browned and crispy around the edges, flip the patties. Top each patty with a slice of cheddar cheese. Once the cheese melts, stack the patties into double burgers.
Toast the buns cut-side down on the griddle until golden. Remove the bottom buns to a cutting board and place the top buns directly on the stacked burgers to warm slightly.
Remove the chili from heat and allow it to cool slightly.
Assemble the burgers: add a heaping tablespoon of slaw to the bottom bun, followed by the double burger patty, a tablespoon of chili, and a drizzle of yellow mustard. Secure with a toothpick if desired. Serve immediately and enjoy.
