How to Make It
In a large saucepan or Dutch oven, heat 2 tablespoons of oil over high heat. Season the meat with salt and pepper. Working in batches, brown the meat all over, about 3 to 4 minutes; using a slotted spoon, transfer the meat to a paper towel–lined plate.
Add the remaining tablespoon of oil to the pan and heat over medium heat. Add the onion, garlic and jalapeño pepper and cook, stirring frequently, until softened, about 3 minutes. Add 6 tablespoons of gochujang, the chipotle pepper, sugar, cumin, coriander and salt; cook, stirring frequently, for 3 minutes. Add the beer, broth and tomatoes; using a wooden spoon, scrape up any browned bits on the bottom of the pot. Bring the chili to a simmer and cook until the meat is very tender, about 2 hours. Let the chili cool to room temperature and season to taste with salt. The chili can be made up to 1 day ahead.
In a small bowl, stir together the sour cream and remaining 2 teaspoons of gochujang.
Arrange the chips on a platter. Using a slotted spoon, scatter a layer of chili over the chips. Sprinkle the cotija cheese over the top. Dollop the gochujang sour cream over the cheese, garnish the nachos with the serrano peppers and serve.