Preheat your oven to 140°C (275°F) / 120°C Fan / Gas Mark 1. This low temperature is key for a slow, even bake that sets the shortbread perfectly.

In a large mixing bowl, rub the cold, chopped butter into the flour, sugar, and salt until the mixture resembles fine breadcrumbs. Alternatively, pulse these in a food processor. Use your hands to gently bring the mixture together into a firm dough, adding a tiny splash of cold water if needed.

Divide the dough in half. Lightly roll each half into a log approximately 6cm in diameter, being careful not to overwork it.

Wrap each log tightly in cling film and chill in the fridge for at least 1 hour until firm.

Once chilled, unwrap the dough logs and slice each one into 8 equal circles.

Arrange them on two large baking trays lined with baking parchment, leaving a little space between each biscuit for spreading.

Bake for 35–40 minutes, or until the biscuits are a pale golden colour. You may want to rotate the trays halfway through cooking to ensure they bake evenly.

As soon as you remove the biscuits from the oven, take half of them (8 total) and cut a small hole in the centre using a 3cm cutter or the smallest one you have.

Work quickly while they are still hot and soft. Leave all biscuits to cool completely on the trays.

While the biscuits cool, prepare the filling.

In a mixing bowl, beat the softened butter and vanilla seeds until creamy. Gradually beat in the sifted icing sugar until you have a smooth, light buttercream.

To assemble, turn the solid biscuits (the ones without holes) upside-down. Gently spread a layer of buttercream on each, leaving a small well in the centre. Spoon 1 tsp (5 ml) of raspberry jam into the well. Carefully place a biscuit with a hole on top of each one to create a sandwich.

Finish with a light sprinkle of caster sugar.

Cut the centre holes immediately after baking while the biscuits are still hot and soft on the tray. This is the secret to getting a clean cut without cracking or breaking the delicate shortbread.