Preheat the oven: Set it to 375°F (190°C).
Lightly grease a standard muffin tin.
Form the cheese rounds: On a parchment-lined baking sheet, make 12 small mounds of cheese (about 2 tablespoons each). Flatten slightly into 3-inch circles.
Bake the cheese: Bake for 6–8 minutes until the edges are deep golden and the centers are bubbly. They should look lacy and crisp around the edges.
Shape the cups: Let the cheese rounds cool for 30–45 seconds to firm up, then quickly lift each one and press into the muffin tin wells to form cups.
Let them cool in the tin until firm.
Cook the filling: Heat a skillet over medium-high. Add the ground beef and onion. Cook, breaking up the meat, until browned and the onions are soft, about 6–8 minutes.
Drain extra fat if needed.
Season it up: Stir in garlic, taco seasoning, tomato paste, and water or broth. Simmer 2–3 minutes until thick and saucy. Season with salt and pepper.
Assemble: Gently remove cheese cups from the muffin tin.
Spoon warm taco filling into each cup.
Add toppings: Finish with lettuce, tomatoes, jalapeños, avocado, sour cream, and cilantro. A squeeze of lime wakes everything up.
Serve: Enjoy right away while the cups are still crisp.