Preheat the oven to 150C/ 200F/ GM 2.
Lightly grease a 20x20cm (8x8-inch) square deep-sided baking tin and line it with baking parchment.
Put the flour, semolina, sugar and salt into a basin and mix. Cube the butter, add to the bowl.
Use your fingers to rub the butter in. At first it will resemble breadcrumbs, but keep on working the ingredients until a dough forms.
Press the dough into a prepared baking tin and level the surface using your fingers and/ or the back of a metal spoon.
Prick the dough all over with a fork and bake for around 40 minutes until golden, turning the tin around halfway through the cooking time to ensure an even bake. Leave to cool in the tin.
Melt the Biscoff spread, either in a saucepan over low heat (stirring constantly) or spoon it into a heatproof bowl and microwave on low for 10-20 seconds. Stir until smooth, pour it over the shortbread and leave it to set.
Melt the chocolate, either in the microwave or over a bain-Marie, spread it over the Biscoff layer and top with sprinkles.
When the chocolate has almost fully set remove the traybake from the tin and use a sharp knife to cut your Biscoff caramel slices (aim for around 16 pieces).