Preheat the oven to 170°C / 325°F / Gas Mark 3.
Work the flour, baking powder, salt, vanilla seeds and butter, cut into small pieces, together with your hands until you have a coarse sandy texture.
Add the sugar and rub it through.
Make a well in the dough, put the egg yolks in it, cover them with dough mixture and crush them with the palm of your hand.
Cover with mixture again and repeat until the egg yolks are completely incorporated (take care not to overwork the dough).
Lightly flatten the ball of dough, cover with plastic wrap and set aside for 1 hour in the refrigerator.
Flour your work surface and rolling pin and roll out the dough to a thickness of 1 cm (½ inch).
Cut 12 circles using the pastry rings and place each biscuit, still inside its ring, on a baking tray lined with baking paper.
Refrigerate for 20 minutes to firm the dough.
Bake in the preheated oven for 10–12 minutes.
When the biscuits are baked and nicely browned, let them cool for 15 minutes before removing the rings.
Wash the strawberries, hull them and cut them into rounds.
Spread six shortbreads with a large scoop of frozen yoghurt, then top with the sliced strawberries.
Place a thin layer of frozen yoghurt on top, cover with a second shortbread and press down to spread the frozen yoghurt over the whole surface.
Smooth the sides of the sandwiches with a knife to trim any overflow.