Add the egg, baking powder, salt and vanilla and beat until well combined. Add the flour and mix until combined.

Divide the dough in half and place each half between 2 sheets of wax or parchment paper. Roll out to around 1/4- inch thick and keeping the paper in place, transfer the dough to a baking sheet. Refrigerate for around 30 minutes.

Preheat the oven to 350 F and position the rack in the middle of the oven. Line 2 baking sheets with parchment paper.

Working with 1 portion of the dough at a time, carefully peel away the top layer of wax or parchment paper and cut the cookies into round shapes using 3-inch cookie cutters. Cut a heart shape with a small heart cookie cutter out of the centre of half if desired. Transfer the cookies to the prepared baking sheets with a metal spatula and bake for around 6 to 9 minutes, one sheet at a time, until light brown around the edges, rotating the pan half-way through. Repeat with the remaining dough, re-rolling the scraps.

Cool the cookies on a wire rack and sprinkle half of the cookies with icing sugar if desired (the ones with the cut outs, if applicable). Spread the underside of half of the cookies with a dollop of jam spread to the edges and top with a second cookie to create a sandwich. Repeat with the remaining cookies. Store at room temperature for up to 1 week in a sealed container or in the freezer for up to 1 month.