Sift the flour, baking powder and salt into a bowl and set aside.
In an electric mixer add the sugar and butter and beat on medium speed until fluffy. Mix in the vanilla and egg. Reduce the speed to low and slowly add the flour mixture until well combined. Halve the dough and refrigerate for 2 hours.
Preheat the oven to 180 degrees C. Line a baking tray with baking paper.
Roll out the dough to 4mm thickness then cut out full hearts, re-roll scraps and cut again. With the second ball of dough cut hearts again, but this time cut out the centres.
Lay the hearts well spaced on the baking tray then bake for 8 to 10 minutes until pale golden. Transfer to a rack to cool.
If desired warm the jam so it spreads well and thin. Or keep cold for thick jam centres.
Dust the hearts with the heart whole with the icing sugar. Spread the complete heart with the jam. Sandwich the two together to create the finished biscuit as per the picture.