Place potatoes into a large saucepan, and fill with enough water to cover. Bring to a boil, and cook until tender, about 10 minutes. Drain.
While the potatoes are cooking, crumble the ground beef into a skillet over medium-high heat. Cook for a few minutes, then stir in the onion. Cook until meat is no longer pink, and the onion is tender. Drain excess grease, and gently stir in the potatoes. Season with salt and pepper to taste.
Place the tomatillos, garlic, jalapeno, and cilantro into a blender. Squeeze avocados out of their skins into the blender. Process until smooth.
Heat tortillas in a skillet until warm and flexible. Spoon on some of the meat mixture, and top with the sauce. Roll up, and enjoy.
