For 60 biscuits
1. For the caramel, heat the milk and sugar together slowly until the sugar has dissolved. Cook for around 45 minutes to reduce, stirring occasionally (do not boil or allow to burn)
2. When the milk slowly begins to turn golden, add a pinch of bicarbonate of soda and a pinch of vanilla and reduce to a thick caramel, stirring continually. This will take around 15 minutes. Leave to cool; it will develop a thicker consistency suitable for piping.
3. Heat the oven to 190°C (170°C in a fan oven), 375°F, gas 5 and line a baking tray with grease-proof paper.
4. Sieve the flour into a bowl and mix with the cocoa and salt. Cream the butter and sugar together and stir in the egg yolks, cream and vanilla seeds. Tip the flour mixture on top and knead to a smooth dough. Use a teaspoon to take small portions of the dough and shape into small balls. Roll in sugar and place on the baking tray, leaving a gap between.
5. Use your thumb or the end of a wooden spoon to make a dent in the center of each biscuit. For the peanut butter and jelly biscuits, spread a little peanut butter in 1/3 of the biscuits. Bake in the oven for around 10 minutes.
6. Take out of the oven and, if necessary, reshape while still hot. Cool on a wire rack.
7. Stir the caramel cream thoroughly and spoon into a piping bag with a star nozzle. Pipe into 1/3 of the biscuits.
8. For the chocolate and jam biscuits (bottom left), melt the chocolate in a bowl over hot water and put a little into the remaining unfilled biscuits. Leave to dry. When dry, top with 1 tsp of red jam.
9. For the peanut butter and jelly biscuits, warm the blackcurrant jelly in a small saucepan. Add a little to the cooked peanut butter biscuits and leave to dry.