Preheat oven to 180°C and line the base and sides of a 20cm square baking tin.

In a food processor, combine the flour, salt and sugar. Add the chunks of butter and process until it forms large clumps - may a minute or so. Press the dough firmly and evenly into your baking tin with floured fingers. Bake for 15 minutes or until very pale golden.

In your food processor (don't bother washing it out), grind the pistachios, flour, salt, and sugar to a powder (or as fine as you can make it!). Add the butter and process until no longer visible. Add egg and vanilla, blending until it forms a smooth paste.

Spread the filling over the cooked base. To decorate like I have in the photos, cut the apricots into diagonal strips, then slide each half onto a knife and fan over the pistachio frangipane. Alternatively, you could put the halves straight on or cut the apricots into slices and decorate as you wish.

Bake the slice for 50 minutes, or until they are golden and a skewer inserted into the pistachio comes out clean. Leave in pan to cool.

Dust with icing sugar to decorate and cut into squares. I couldn't wait for them to cool and cut them while still warm - and they were amazing - but Deb recommends to rest them in the fridge to cool completely before cutting.

Keep left over slice in the fridge.