We all know that ripe, summer raspberries produce the most delicious jam – here it’s sandwiched with a buttercream filling between crisp biscuits. The swirl is optional (if you have a patterned stamp), but it does make for an extra-professional finish.
Make the jam. Place the raspberries in a small, deep-sided pan and crush them with a potato masher. Add the sugar and bring the liquid to the boil over a low heat until the sugar dissolves. Then, increase the heat and boil for 4 minutes. Remove the pan from the heat and pass the jam through a sieve into a heatproof bowl. Discard the seeds in the sieve. Leave the jam to cool, then chill it to set.
Heat the oven to 170°C/150°C fan/325°F/Gas 3.
Make the biscuits. Place the butter and caster sugar in a mixing bowl and beat well for 3–5 minutes, until pale and fluffy. Add the egg and vanilla and beat again until thoroughly combined.
Sift in the flour and cornflour and mix by hand to a crumbly dough. Bring the dough together with your hands and knead it gently on a lightly floured work surface until smooth. Do not overwork.
Halve the dough and shape each half into a flat disc. Wrap the discs and chill them for 20 minutes.
Unwrap one of the dough discs on a lightly floured work surface and roll it out to about 3mm thick. Using the fluted round cutter, cut out 12 rounds, re-rolling the trimmings as necessary.
Lightly flour a biscuit stamp, if you have one, then stamp each round to create a pattern. Re-cut the rounds with the fluted round cutter, then place the 12 discs on one of the lined baking sheets. Chill them while you roll out the remaining dough.
Repeat steps 6 and 7 with the remaining dough disc, then, using the heart-shaped cutter, stamp out the centre of 12 of the rounds. Place these on the other baking sheet and chill them for 20 minutes.
Bake the biscuits for 10–12 minutes, until the edges start to turn a pale golden colour. Leave them to cool on the baking sheets for 5 minutes, then transfer the biscuits to a wire rack to cool completely.
Make the filling. Put the butter into a bowl and sift the icing sugar on top. Add the vanilla and, using a wooden spoon or an electric hand whisk, beat until very light and smooth.
Dollop a spoonful of the filling onto the smooth side of each of the 12 plain biscuits, spreading it to the edges with a palette knife. Spoon a little jam over the buttercream, then sandwich, smooth side downwards, with the 12 cut-out heart biscuits. Dust with icing sugar to serve.