In the bowl of a food processor, place the flour, sugar and salt. Pulse.
Add the butter and pulse using quick bursts, until the butter pieces are no larger than small peas. Add the egg yolks, water and vanilla and pulse just until the dough comes together.
Transfer the dough to a piece of parchment paper and roll it about 4 to 5mm thick.
Using a template, cut out 2 letters or numbers with a sharp knife. Transfer to a cookie sheet and refrigerate for 20 minutes.
Preheat oven to 180°C. Bake for about 15 minutes or until the edges start to brown. Let cool completely.
Beat all the ingredients for the filling until the mixture forms stiff peaks.
Transfer the filling into a piping bag and pipe dollops of the cream beginning with the inner and outer edges of the cookie. Place the second cookie on top and repeat the process with the filling.
Decorate with your favourite toppings and keep refrigerated before serving.