Preheat the broiler. Using a food processor or a stand mixer fitted with the meat grinder attachment, grind the meat. Preheat a cast-iron skillet over medium-high heat. In a bowl, mix together the meat, onion, parsley, egg yolk, salt and pepper. Form the mixture into 4 patties.
In a 12- to 13-inch casserole, arrange the tortilla chips in an even layer. In a small pan, heat the refried beans and stir in the beef stock to thin them a little; season with the cumin. Dollop the refried beans on top of the chips, then top with tomatoes and cheese. Bake in the center of the oven until cheese has melted, 12-15 minutes.