Line an 18 x 9.5cm (7 x 3.75in), deep round cake tin with baking parchment. Preheat the oven to 180°C (fan oven 160°C), gas mark 4.
Put all the cake ingredients, except the coffee, in a large bowl and using an electric whisk (mixer or hand-held), beat together until very smooth and creamy. Dissolve the coffee in 1 tbsp of boiling water and blend in.
Spoon the mixture into the tin and bake for about 45-55 mins or until golden and firm to touch. A skewer pushed into the centre should come out clean. Cover loosely with foil if it begins to darken before the cake is cooked. Cool in the tin for 30 mins before turning out onto a wire rack.
Meanwhile, make the caramel cream. Whip the double cream until it just begins to thicken and hold its shape. The whisk will leave a trail when lifted.
Change to a balloon whisk (to avoid over-whipping) and add 2 generous tbsp of confiture de caramel. Whisk until the cream again holds its shape. Add a further 2 tbsp of caramel and whisk again until the cream retains its shape. Continue until all the caramel has been incorporated into the cream and the cream forms soft peaks. Divide the cream between two bowls.
Cut the cake in half, then split each half again to give four equal rounds. Put the round, which was the top of the cake, cut side up on a serving board or plate. Take one bowl of caramel cream and spread about a third over the cake, right to the edge. Top with a second round and repeat until all the cream is used. Finish with the round that was the base of the cooked cake, cooked side up, as this is the flattest. Press down lightly.
Spread the remaining bowl of cream over the top and sides of the cake. Decorate with shards of white chocolate and mini Easter eggs.
To make the chocolate shards, melt 200g (7oz) good-quality white chocolate over a pan of gently simmering water. On a clean baking sheet, spread the chocolate into a round about the thickness of a pound coin and chill for 1 hour. With a large, sharp knife, cut wafer thin slices off the round, starting at one edge of the chocolate. As you make the shards, pop them into a container and into the fridge or freezer to keep firm.