Preheat oven to 180 degrees C and line two baking trays with baking paper.
In a bowl, beat butter and sugar until creamy. Beat in vanilla and egg.
Sift together the flour, salt and baking powder. Add to butter mixture and beat until well blended. Place dough on a floured surface and knead until smooth. Wrap in plastic wrap and chill 30 minutes.
Roll out the dough on a floured surface. Cut out heart-shaped cookies. Place on baking trays with a little space between them and bake 7 minutes or until edges are lightly browned. Let cool completely before removing from trays.
Place the diced chocolate in a bowl. Heat the cream in a small saucepan until simmering. Pour over the chocolate. Let stand 3 minutes then stir until smooth. Dip each cookie in halfway and return to baking paper to set.