Preheat the oven to 190C/375F/Gas 5.
For the shortbread, place the butter, flour, icing sugar and egg yolk into a food processor and pulse until the mixture comes together as a dough.
Turn the dough out onto a lightly floured surface and roll out to 0.5cm/¼in thick. Use a pastry cutter to cut rounds out of the dough and place onto a non-stick baking sheet.
Transfer to the oven and bake for 8-10 minutes, or until lightly golden-brown. Remove from the oven and allow to cool.
For the filling, place the cream into a large bowl with the icing sugar and vanilla seeds and whisk until soft peaks form when the whisk is removed. Gently fold in the strawberries.
To serve, use the cream filling to sandwich the shortbread biscuits together and place onto a serving plate. Dust with icing sugar and garnish with extra strawberries.