Set a very large (12-inch) skillet over medium heat and add the chorizo. Cook, breaking up the clumps, until browned and thoroughly cooked, about 8 to 9 minutes. Remove from the skillet (leaving behind as much fat as possible) and set in a warm spot.
To the skillet, add 1 or 2 tablespoons of the oil (depending on how much fat the chorizo has rendered) and the onions. Cook for several minutes until the onions are soft, then add the beans and their broth. As the beans come to a simmer, mash them to a smooth paste with a bean masher, old-fashioned potato masher or the back of a large cooking spoon. Cook, stirring nearly constantly, until the consistency of very soft mashed potatoes—expect about 10 minutes depending on how brothy the beans are. Taste and season with salt if you think necessary. Keep warm over the lowest heat, preferably covered to keep the beans soft and moist.
Into a large (10-inch) non-stick or well-seasoned cast-iron skillet set over medium heat sprinkle the cheese. When the cheese is completely melted, sprinkle with the chorizo. Stir everything together. (If you want to make crispy choriqueso, do it in two batches: when the cheese melts, sprinkle it with chorizo and let it cook over medium heat until it becomes crispy on the bottom. Roll it up, cut drain off the excess fat, then slide it onto the cutting board. Do the same with the other half of the cheese and chorizo. Cut each roll in half to use and use a portion in each torta.)
Heat a large griddle or skillet over medium. Slice the rolls open lengthwise. If using bolillos, remove some of the soft bread in the center of each piece, making a small hollow. Brush the insides with the oil, then lay them cut-side down on the griddle or skillet to crisp to a rich golden brown, about 2 minutes. (You may have to do this in batches if your rolls are large or griddle/skillet small.)
Smear about ¼ cup of the bean mixture over the bottom half each roll. (You’ll have about 1 cup of the mixture leftover; cover and refrigerate for a midnight snack.) Top with the cheese and chorizo mixture, and finish with the avocado. Dash on the hot sauce or spoon on the salsa. Set the top of each roll in place and you’re ready to serve.