Heat 1/4 cup of oil in a large skillet over medium heat. Add the onion and 3 cloves of garlic and cook until lightly browned, 3 to 4 minutes. Discard the onion and garlic. Add the ground bean mixture and enough water (use the bean cooking water, if any remains) to thin to the consistency of an enchilada sauce, cooking until blended and heated through.
Meanwhile, stack the tortillas, wrap them in wax paper or parchment paper and microwave to soften, 2 minutes. Heat the remaining 3/4 cup oil in a skillet to 350 degrees. Fold the tortillas in quarters and fry, one at a time, for a few seconds each side. Do not allow them to become crisp. Drain on paper towels.