Make the sautéed onions: In a sauté pan, heat the oil over medium-high heat. Once the oil is hot, add the onion slices. Stir occasionally so they don’t stick or burn. Cook until the onion is tender and slightly caramelized, 10 to 12 minutes. Then season it with the Black Chile Coffee Cocoa Rub and set aside.
Fire up your grill. Heat the grill to 225°F to 250°F.
Make the burgers: Divide the ground chuck into 8 equal portions (4 ounces each) and form each into a 1-inch thick patty.
Char the peppers: Use grilling tongs to lightly brush the grill grate with a canola oil-soaked cloth. Place the jalapeños on the grill until evenly charred and black, turning them every 2 minutes for 10 to 12 minutes.
While the peppers are still hot from the grill, place them in a bag and close it, or place them in a bowl and cover with plastic wrap. Allow the peppers to steam for about 5 minutes. Take the peppers out of the bag and use a spoon or gloved fingers to remove the skin. Discard the skin, stems, and seeds (and take care not to touch your face or eyes).
Crank the heat on the grill up to between 400°F and 450°F, by opening the vents three-fourths of the way for a few minutes. Once the temperature has risen, close the vents slightly to maintain temperature and avoid flare-ups.
Cook the burgers: Season both sides of the patties with the Black Chile Coffee Cocoa Rub, place them on the grill and close the top.
Cook until each side has developed a slight brown crust, and some dark grill marks, about 3 to 4 minutes per side. Put cheddar cheese on 4 of the patties and white American cheese on the remaining 4 patties.
Split and toast the potato rolls on the grill, flat side down, for 30 to 45 seconds, depending on your preference of doneness. Spread the 1,000 Island dressing on both the top and bottom buns. Stack a cheddar-topped burger on top of an American cheese-topped burger on each bun. Top with the sautéed onions, bacon, and The Other Sauce. Place the top bun on top and serve with the grilled jalapeños on the side.