Rinse and sort the Dried Pinto Beans under cold water, removing any stones; then soak them overnight in plenty of water, or use a quick-soak method (bring to a boil for 2 minutes, remove from heat and let sit 1 hour).
Drain the soaked beans and transfer to a large pot; add fresh Water to cover by about 2 inches, then tuck in a halved White Onion and a few smashed cloves of Garlic. Bring to a boil, reduce heat, and simmer gently until the beans are very tender, about 1 to 1 1/2 hours (or 20–30 minutes in a pressure cooker).
When the beans are tender, remove and discard the onion halves and garlic pieces (or stir them into the beans if you prefer more texture) and reserve 1 to 2 cups of the cooking liquid. Taste and season with Salt to your liking.
Heat about 2 tablespoons of Lard in a large skillet over medium heat. Add a ladle of the drained beans and cook briefly to warm through, then begin mashing them in the pan with a potato masher or the back of a spoon.
Add more beans and a splash of the reserved cooking liquid as needed while you mash until you reach a creamy but chunky refried-bean consistency. Adjust salt and cook off any excess moisture so the mixture is spoonable but not soupy.
Warm the Flour Tortilla in a dry skillet or wrapped in a damp towel in the microwave until pliable. Place a generous spoonful of the bean mixture in the center of each tortilla and top with shredded Oaxaca Cheese.
Fold the sides of the tortilla over the filling and roll tightly to form burritos. If you like, melt a little extra lard in the skillet and sear each burrito seam-side down, then turn to brown the other side until the tortillas are golden and the cheese is fully melted, about 1–2 minutes per side.
Serve the burritos hot, optionally with salsa, chopped cilantro, or a squeeze of lime. Leftover beans keep well in the fridge and make great next-day filling.
