Lightly oil a 9x13 baking pan and set aside.
In a medium-sized saucepot, over medium heat, add the olive oil and minced garlic. Sauté for a few minutes until onions are translucent.
Add the fire-roasted tomatoes to the onions and garlic with any liquid in the can. Stir to combine.
Add the chopped green chilies, cumin, oregano, and Kosher salt. Bring to a boil and reduce heat to a low simmer for 30 minutes. Use an immersion blender to puree the tomatoes to the desired texture.
Add the can of tomato sauce and simmer for another 20 minutes.
Add the chopped cilantro and stir to combine.
Remove sauce from the heat and add ½ cup of sour cream. Stir to combine and set aside.
In another saucepan over medium-low heat, add 2 cups of shredded cheese and ½ cup of sour cream. Stir constantly until the cheese is melted and the sauce is creamy. Stir in the shredded chicken.
Fill the tortillas with the desired amount of chicken mixture and place them seam-side down in a prepared 9x13 baking pan. Cover with approximately ½ of the tomato sauce, reserving the extra for serving.
Cover the pan with parchment and bake at 350-degree oven for 30 minutes. Remove from oven and top with ½ cup of shredded cheese and bake for another 8-10 minutes.