For the chipotle ketchup: Pour the ketchup, vinegar, chipotles and adobo sauce directly into a food processor and run until pureed.
For the tomatillo relish: Mix together the tomatillos, cilantro, lime juice, vinegar, sugar, salt, garlic, jalapenos and onions in a large mixing bowl until well combined. Cover and refrigerate for 1 hour to allow the flavors to marry.
For the cornbread buns: Mix together the milk, butter, cornbread mix and egg in a medium bowl until combined, and then set aside to rest for 5 minutes.
Heat a medium nonstick skillet or cast-iron griddle pan over medium-high heat. Spray with cooking spray and spread 1/3 cup of the batter into the heated skillet with the bottom of a spoon or measuring cup, making sure the cornbread bun will be big enough to fit the length of the hot dog. Cook the cornbread until you start to see the batter bubble on the top and brown around the edges, about 2 minutes, and then flip and cook until golden brown, about 1 minute longer. Repeat with the remaining batter.
To serve, place a cornbread bun on a plate and top with the grilled hot dog, Chipotle Ketchup, Tomatillo Relish, crushed tortilla chips and cotija cheese. Repeat with the remaining hot dogs.