Combine the cornmeal, warm water, cumin, cheese, butter and salt, mixing thoroughly.
Let mixture stand for five minutes.Knead with your hands for about 3 minutes moistening your hands with water as you work. Preheat the oven to 375 degrees F.Form small balls with the dough. Spray your muffin tin with non-stick spray.
Place one ball in each muffin cup and press with your fingers to make small shells.Meanwhile mix the avocado, lime juice, salt and pepper in a small bowl. Set aside.
Bake for about 20 minutes.
Place them on a serving plate, then fill each bite with shredded beef and garnish with avocado pieces and cilantro leaves.