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 until the skin begins to bubble and darken, 6 to 10 minutes per side. 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, vinegar, onions, cilantro, mayonnaise, scallion, chili powder, garlic, salt, pepper, and tomatoes in a medium bowl.
Put on disposable gloves and remove as much of the poblano pepper skin as you can. 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 pepper pieces into the bowl with the remaining relish ingredients. Refrigerate until the burgers are ready to be assembled and cooked.
Combine the Cheddar cheese and cream cheese in a small bowl. Divide the mixture into four ¼-inch disks. Divide the ground beef into eight 4-ounce balls. Flatten each ball into a ¼-inch 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 for the remaining disks.
To cook the burgers, preheat a grill to medium-high. Place the burgers on the grill and cook, without pressing down, for 4 to 6 minutes on each side for medium doneness, or longer if you prefer a more well-done burger. While the burgers are cooking, place ½-cup of the lettuce and ½-cup of the 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 ½-cup of the relish. Finish each burger with a bun top.