I first had this sandwich at a small restaurant in Telok Ayer Street in Singapore, and immediately went home to duplicate the recipe. In this recipe, I've used Camembert cheese. However, any other soft cheese would do just fine. A great option for vegetarians too :)
Toast the 2 slices of sourdough bread using a bread toaster.
Spread the top of one bread slice with the pesto sauce. On the other bread slice, place the sliced camembert cheese, and let it melt using the toaster.
Place the tomato slices and truffle slices, and close up the sandwich.
In a medium skillet, heat about 1 teaspoon of butter over medium-low heat until just melted. Cook on each side for about 5-6 minutes on a low heat or until each side is a nice crispy golden brown.