Heat the oil in a skillet over medium heat and brown the onion for 3 minutes.Add the mushrooms and cook for 3 more minutes.Add the tuna, cream cheese, milk and mix well.Season with salt and pepper to taste and remove from heat.
Add the olives, mix them and little by little add the pasta.Stir it well and place it in a previously greased baking dish.Add the Parmesan cheese, the Taqueritos and the chives on top.Cover the pan with aluminum foil and bake for 25 minutes.Remove the foil and bake for 5 more minutes.
