In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté until it becomes translucent, about 3-4 minutes. Next, add the minced garlic and sauté for another minute until fragrant.
In a mixing bowl, combine the sautéed onions and garlic with the shredded chicken, corn, salsa, sour cream, and Tex Mex cheese. Season with salt and pepper to taste. Mix until everything is evenly coated.
Preheat your oven to 400°F (200°C). Brush both sides of each tortilla with melted butter. Place about 2-3 tablespoons of the filling in the center of each tortilla, then roll it up tightly.
Arrange the rolled flautas seam-side down on a baking sheet. Brush the tops lightly with more melted butter. Bake for 20-25 minutes or until they are golden brown and crispy.
While the flautas are baking, prepare your toppings. Dice the avocado and tomato, slice the jalapeno, and chop the cilantro. In a small bowl, combine the lime juice with a pinch of salt.
Once the flautas are baked to perfection, remove them from the oven. Serve them hot with your selected toppings and enjoy the crispy, cheesy goodness!