Preheat the oven to 400° F and place an oven rack in the center of the oven.
Heat a 10-inch skillet (cast iron or non stick works best) over medium heat. Add the oil and twirl the pan to evenly coat, making sure to coat the sides of the skillet. Add the scallions, and cook for about 1 minute, or until they begin to wilt. Stir in the taco meat and cook for a minute, followed by the cherry tomatoes.
Quickly whisk together the eggs, half and half, salt, pepper, and the parmesan cheese, then pour the eggs into the skillet. Using a spatula, move the edges of the eggs towards the center of the pan, stirring around the curds as they form. Sprinkle with pepper jack cheese, nestle in half the avocados, and sprinkle with 1/4 cup cilantro and half of the jalapeno slices on top. Place in the oven to bake for about 15 minutes, or until the frittata is lofty and the center is no longer runny when you insert a knife. Remove from the oven, let it stand for a few minutes before slicing and serving.
Serve with cotija cheese, red onion, sour cream, remaining cilantro and jalapeno, and tortilla chips.