Place all the ingredients for the compote in a small saucepan over medium heat. Bring to the boil, making sure the sugar has dissolved. Allow to simmer for just a few minutes until the berries start collapsing a bit. Set aside to cool while you make the pain perdu (French toast). Lightly beat the egg and milk together, then pour into a shallow plate. Using a thick based skillet or frying pan over medium to high heat, melt the butter in the pan. Dip each slice of bread briefly into the egg mix, then place into the pan and fry on each side until lightly browned. Place the slices of cheese onto two slices of the toast, top with the other two slices of toast and return the sandwich to the pan with a bit more butter. Continue cooking until the cheese in the middle turns gooey and starts oozing out the sides of the bread. Place one sandwich on a serving plate, cut in half to make triangles, place on top of each other and then drizzle with a ladle full of the warm berry compote. Dust lightly with icing sugar and tuck in while the cheese is still oozy.