Add flour and sugar to a food processor or mixing bowl and mix until evenly distributed.
Then add butter to the food processor and process until the mixture resembles fine breadcrumbs. If you’re using your hands rub the butter into the flour and sugar mixture.
Add a few tablespoons of water (or milk) and mix together until the pastry dough has formed. Use your hands to bind the dough together.
Wrap the sweet shortcrust pastry in clingfilm and leave to chill in the fridge for at least 15 minutes.
Preheat your oven to 180°C (gas mark 4, 160°Fan)
On a floured surface, use a rolling pin to roll the pastry 5mm (0.5cm) thick and lay it over the base of a greased or lined tart tin. Trim away any excess pastry, it should only be covering the bottom. With a fork, prick the pastry base.
Place a layer of parchment paper on top of the pastry and add baking beans. Blind bake in the oven for 10 minutes or until slightly golden brown. Once baked, leave the pastry to cool down and set aside for later use.
Frangipane Sponge
Place butter and sugar into a large mixing bowl and cream together until light and fluffy.
Add a beaten egg and almond extract to the mixing bowl and mix together until evenly combined.
Pour flour, baking powder and ground almond into the mixing bowl and mix together until evenly distributed.
Assemble Almond Slice
In a small mixing bowl, mix the jam to remove any lumps and for it to spread easily. Add an even layer of raspberry jam on top of the pastry.
Pour the frangipane sponge mixture over the layer of jam and spread until evenly distributed. Be careful not to mix the cake batter into the layer of jam.
Sprinkle flaked almonds on top of the sponge mixture and bake in the oven for 30 to 35 minutes or until cooked through and the top is golden.
Once baked, let the almond slice cool then cut into traditional rectangle slices (or any shape you like).
Video
Notes
I prefer using almond extract to almond essence. Almond extract is made from natural ingredients whereas almond essence uses artificial flavourings to create an almond flavour.I prefer lining my baking tin with parchment paper to greasing it with butter. The jam can caramelise to the sides of the tin and can be difficult to remove once cool. If you use parchment paper, you can simply lift it out of the tin.