Somewhere between a Bakewell tart and a Viennese whirl, and with a slight boozy note, these melt-in-the-mouth biscuits make a delicious alternative to chocolates at the end of a meal.
Make the cherry jam. Put the cherries and lemon juice in a small saucepan. Add the sugar and slowly bring to the boil over a low heat. Crush the cherries and sugar together using a potato masher, then when the sugar has dissolved, increase the heat and boil for another 4 minutes, until the temperature of the jam reaches 105°C/221°F on the sugar thermometer. Remove from the heat and leave to cool and set.
Make the marzipan. Mix the caster sugar, icing sugar and ground almonds together in a large bowl, then stir in the vanilla paste and, a little at time, add the beaten egg, mixing until the ingredients have come together as a thick paste. (You may not need all of the beaten egg.)
Turn out the paste onto a work surface lightly dusted with icing sugar and knead until smooth. Roll the marzipan into a ball, then wrap it in cling film and chill until needed.
Make the biscuits. Heat the oven to 190°C/170°C fan/375°F/Gas 5. Beat the butter and icing sugar in a stand mixer fitted with the beater, on medium speed for 3–5 minutes, until pale and creamy.
With the mixer still running, add 55g of the marzipan in small pinches until fully incorporated. Reserve the remaining marzipan for later.
A little at a time, add the eggs and egg yolks, beating well between each addition. Add the vanilla seeds and salt, beat again.
Sift the plain flour and cornflour together into a bowl. Tip the dry ingredients into the egg mixture and beat on a low speed until fully incorporated. Spoon the mixture into the medium piping bag fitted with a large round nozzle and twist the end to seal.
Pipe 12 biscuits each 4cm in diameter on each lined baking sheet, leaving at least 2cm between each biscuit. Bake for 15–20 minutes, until golden brown. Remove from the oven and leave to cool on the baking sheets.
While the biscuits are cooling, make the filling. Loosen the remaining marzipan with the kirsch, stir in the jam and mix until fully incorporated.
Once the biscuits are completely cool, spoon a little of the marzipan filling onto the underside of 12 biscuits. Sandwich the filling using the remaining (plain) 12 biscuits.
Melt the dark chocolate in either the microwave or a heatproof bowl set over a pan of barely simmering water.
Spoon the melted chocolate into the small piping bag fitted with the writing nozzle and pipe fine lines across the biscuits, then leave them to set for about 10 minutes before serving.