Preheat oven to 400°
Lightly spray a 8x8 baking dish with a nonstick cooking spray.
Place potatoes in baking dish and roast for 45-50 minutes or until potatoes are tender.
While potatoes are roasting, add ground beef, onions and jalapeños to a large skillet or frying pan and cook over medium high heat until meat is no longer pink.
Add garlic and cook for another minute or two. Drain and return to pan.
Sprinkle taco seasoning over meat and add water and corn. Stir frequently and cook until hot.
Remove potatoes from oven and spoon meat mixture over potatoes.
Sprinkle both types of cheese over the top and bake until cheese has melted, about 5 minutes.
Spoon into individual serving bowls and top with diced avocado, sour cream, cilantro, and green onions, if desired.