Add 2 Tbsp butter to skillet or nonstick pan. Heat on medium until melted and starting to bubble.
Using remaining 2 Tbsp of room temp butter, butter both sides of each slice of bread.
Lay first 2 slices of bread in the pan.
Start layering your ingredients, on each sandwich start with 2 slices cheese, apple slices, two remaining slices of cheese and then the arugula.
Place top piece of bread on top.
Continue to grill until golden brown.
Carefully flip the sandwich over and grill on second side until golden brown.
GARNISH (optional):
Spear the pickles and poke into top of the sandwich.
Serve immediately