BUTTER the outside of each piece of bread.
SPREAD Camembert on the inside of one piece of the bread.
LAYER the pear slices, arugula and prosciutto (if using) onto bread.
TOP with final slice of bread.
HEAT a pan on medium-low heat.
PLACE your sandwich into the pan.
FLIP the sandwich when bread starts to turn golden brown - be careful, Camembert is a soft cheese and will melt quickly!
REMOVE from the pan once both sides of your bread are toasted and the cheese is fully melted.