Place butter into a medium saucepan over medium heat to melt. Once melted, whisk in flour until smooth. Slowly whisk in chicken broth. Heat and stir until thick and bubbly. Once thick, stir in cheese and reduce heat to low. Add Ranch seasoning, cumin, bacon, chicken, green chilies and tomatoes, stirring to combine.
Heat olive oil into a medium skillet over medium heat. Pan-fry tortillas for about 30 seconds each side and place on a paper towel lined plate to drain oil. Continue until all 12 tortillas are pan-fried. You may need to add more oil after a few batches.
For each serving, place a tortilla onto a serving plate. Top with a spoonful of sauce and top with a pinch or two of cheese. Place another tortilla on top and repeat with sauce and cheese. Top with avocado slices and cilantro leaves if desired. Serve warm.