Clean your mushrooms, break off the stems and slice the very tip where it is dry off and discard.  Chop your mushroom stems then chop your jalapeno(s).  Heat 1 (only 1) TBS of your oil in a small saute pan and saute them for about 3 minutes until tender. Remove from the heat and add in your cheeses and mix until combined.  In a small bowl, combine the remaining 2 TBS oil, garlic salt and pepper and mix well.  taste and adjust to your liking...you want the oil seasoned well.  Brush the inside and outside of each mushroom with the oil mixture, stuff your mushrooms and grill over medium heat until the mushrooms are done to your liking (varies on the size of mushrooms used) about 4-6 minutes and serve.