In a large bowl, cream together butter and icing sugar. Beat in egg, vanilla and almond extract. Mix well.
In a medium bowl, stir together flour, baking soda and cream of tartar then blend into the butter mixture. Divide dough into thirds and shape into balls.
Working with 1/3 of dough at a time, roll out dough into desired thickness on a lightly floured surface. For each heart sandwich cookie, cut out 2 10cm hearts. Cut out the center of ONE of the 10cm hearts with the 4cm cutter.
Place each piece separately on an ungreased baking tray, 3 to 4cm apart. Bake in the preheated oven until lightly browned (7 to 8 minutes ). Cool completely on wire rack.
Frost the full bottom cookie with a pink frosting or icing then place an open centered cookie on top to form the sandwich. Also frost the small 4cm hearts and serve as separate cookies.