Heat butter in a non-stick pan. Add half the dark chocolate and stir till both melt. Add condensed milk and take the pan off the heat. Stir well.
Toast almonds and slice. Butter 4 bread slices. Spread the chocolate mixture on the remaining slices. Sprinkle some chocolate pieces and almonds over these slices. Cover with the buttered slices, with the buttered side facing upwards. Heat a sandwich toaster and grease one side of it with some butter.
Place the sandwich in the toaster with the unbuttered side on the greased side of the toaster. Close the toaster and grill till both sides are golden. Cut into triangles and serve hot.