The leafy, floral raspberries and intensely perfumed jam are the stars of these elegant traybake slices. Raspberries, like strawberries, have hints of milk in them, making them a perfect pairing for cream. You could try stirring a little chopped fresh basil into the cream, if you like, to up the ante and add a spicy freshness.
Make the sponges. Heat the oven to 180°C/160°C fan/350°F/Gas 4. Beat the butter and sugar in a stand mixer fitted with the beater, on medium speed for 3–5 minutes, scraping down the inside of the bowl from time to time, until pale and creamy. Add the eggs, a little at a time, beating well between each addition. Add 1 tablespoon of the flour if the mixture starts to curdle at any stage. Add the vanilla.
Sift the flour, cornflour, baking powder and salt into the bowl and mix until just combined. Add the milk and mix again until smooth.
Divide the mixture equally between the lined tins and level with a palette knife. Bake on the middle shelf for 20 minutes, until golden and risen, and a skewer inserted into the centres comes out clean. Leave to cool in the tins for 5 minutes, then turn out the sponges onto a wire rack to cool completely.
Make the filling. Whip the cream, icing sugar and vanilla in a bowl using an electric hand whisk until it holds firm peaks.
Assemble the cakes. Place one of the sponges on the lined baking sheet and spread it with the raspberry jam (recipe below). Arrange the raspberries on top and cover with an even layer of whipped cream. Gently press the second sponge on top. Cover the cake and chill it for 1 hour to make cutting easier.
Dust the top of the cake with icing sugar. Using a long, serrated knife, cut the cake in half, then cut each half into 8 equal slices.
To make homemade jam:
Tip the fruit into a large, heavy-based pan, add the sugar and gently squash the fruit with a potato masher or the back of a wooden spoon, keeping a bit of texture. Stir the fruit gently over a low heat with a wooden spoon until the sugar dissolves. Increase the heat and boil rapidly, stirring to prevent the jam catching, until the jam reaches 105°C on a sugar thermometer. Pour the jam into a warm, sterilised jar, place a wax disc on top and leave to cool completely. Cover with a sterilised lid. Use within 1 month.