Fill a large pot or Dutch oven with water and bring it to a boil over high heat. Add the potatoes and boil for 20 minutes or until they are fork-tender. Drain the potatoes, return them to the pot, and mash them using a potato masher before setting them aside.
Heat one tablespoon of oil in a skillet over medium-high heat, then add the chopped onion and minced garlic, cooking for 1-2 minutes until fragrant and softened.
Add the lean ground beef to the skillet, breaking it up with the back of a cooking spoon as it browns. Stir in chili powder, kosher salt, garlic powder, onion powder, black pepper, and ground cumin, cooking for about 8-10 minutes until fully cooked through before removing from heat.
Incorporate the mashed potatoes into the cooked ground beef mixture, stirring thoroughly until fully combined. Taste the mixture and season with additional salt as needed.
Wrap the corn tortillas in a damp paper towel and warm them in the microwave for about 30 seconds or until hot and pliable. Alternatively, you can warm them on a skillet or comal over medium-high heat.
Working in batches of three, fill one half of each tortilla with about 2-3 tablespoons of the potato and meat mixture, then fold over to create tacos. Pour enough oil into a deep skillet so that it reaches halfway up the tacos; heat over medium-high until it reaches 350-375°F before frying each taco for approximately 45-60 seconds per side until golden brown and crispy.