To prepare the relish, preheat the broiler. Spray the poblano peppers with cooking spray and place them on a baking sheet. Place the sheet on the top rack of the broiler and cook the peppers for 6–10 minutes per side, or until the skin begins to bubble and darken. Remove the peppers from the oven, place them in a bowl, and cover the bowl with plastic wrap. Set aside for 10 minutes.
In the meantime, combine the salsa, onion, cilantro, scallion, garlic, salt, pepper, tomato, vinegar, chili powder, and mayonnaise in a medium-size bowl.
When 10 minutes have elapsed, put on disposable gloves and remove as much of the poblano pepper skin as you can and also remove the pepper-caps and seeds. Run the peeled peppers under cold water to help remove any leftover skin and seeds. Pat the peppers dry with a paper towel, place them on a cutting board, and coarsely chop. Fold the pieces into the bowl with the remaining relish ingredients. Refrigerate until the burgers are ready to be assembled and cooked.
To assemble the burgers, combine the cheddar cheese and cream cheese in a small bowl. Divide the mixture into four 1/4'' disks. Divide the ground beef into eight 4–oz balls. Flatten each ball into a 1/4'' disk. Place a cheese disk on top of a beef disk, and then top the cheese with another beef disk. Pinch the burger-seams together, sealing in the cheese. Repeat.
To cook the burgers, preheat a grill to medium-high. Place the burgers on grill and cook, without pressing down, for about 4–6 minutes on each side for medium doneness, or longer if you prefer a more well-done burger. While the burgers are cooking, place a 1/2 cup of iceberg lettuce and a 1/2 cup of crushed corn chips on the bottom of each Kaiser roll. When the burgers are done, place them on top of the fixings and top each burger with a 1/2 cup of relish. Finish each burger with a bun top.
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