Preheat oven to 350 degrees.
Melt the butter. Roll out bread slices between two pieces of parchment paper until very thin. Brush bread on both sides with melted butter. Place 1 teaspoon of the chocolate in the center of each slice. Fold in half diagonally to cover the filling and form a triangle, trim edges. Press the edges with your fingers to tightly seal. Brush tops and bottoms with melted butter crimp edges with fork and sprinkle top with sugar. (At this point, the turnovers can be placed in a zippered plastic freezer bag and frozen for future use.) Place on parchment lined baking sheet and bake for 15 minutes (20 to 25 minutes if taken out of the freezer) or until golden brown. Serve warm or cooled, with raspberry sauce.
In a food processor, puree all ingredients until smooth. Pour puree through a fine sieve into a bowl, pressing on solids, and chill, covered. Sauce may be made 2 days ahead and chilled, covered.;
Recipe courtesy of Sara Moulton