Roast: Preheat oven to 400°F. Prep a baking sheet with foil. Wash and poke holes in the potatoes, coat them in olive oil, salt, and pepper, and bake for 45 minutes.
Brown: While potatoes roast, brown the ground beef with the diced onion in a skillet. Drain excess grease, then stir in the taco seasoning and water. Simmer on low until the liquid reduces.
Melt: In a small saucepan over medium-low heat, combine the Velveeta, Pepper Jack, diced chilies, and evaporated milk. Stir frequently until the sauce is smooth and creamy.
Crisp: Switch the oven to low broil. Bake the potatoes for an additional 15 minutes to achieve a crispy outer skin.
Assemble: Carefully slice the potatoes open and fluff the insides with a fork.
Load: Ladle a generous amount of cheese sauce over the potato, top with the seasoned beef, and finish with your favorite toppings like sour cream or fresh cilantro.