Depending on the size of skillet or flat grill used, one sandwich may need to be made at a time.
Heat a skillet on medium heat and add butter (add half of the butter if making one sandwich at a time).
As the butter melts, lay each piece of bread on the butter just enough to coat each side of the bread.
Lift the bread slightly with a spatula to check if the bottom side of the bread is starting to turn a golden color.
As soon as the bottom sides of the bread are a golden color, turn the bread over and add the cheese on top.
Then top the cheese with jalapenos and salsa. Carefully turn one side of the bread over on to the other one to make a sandwich.
Cover the pan with a lid and continue to cook the sandwich until the outside pieces of bread are lightly browned and the cheese is melted.
Serve right away while warm.