Melt Butter in a frying pan or skillet and add in blueberries. Turn up the heat to high and cook for 5 mins., until they pop. Add in brown sugar and stir until evenly coated.
Continue cooking for 20 - 30 minutes until it starts to thicken. Set aside.
To build the sandwich, spread 4 slices of bread evenly with mascarpone cheese
Evenly layer the remaining slices with brie, spoon on blueberries and top with fresh basil and fresh lemon zest
Preheat Grill | Fry Pan on medium heat
Assemble sandwiches and cook for 8 – 10 minutes per side until golden and crispy