To make the apricot and amaretto preserve, put the apricots and sugar in a saucepan with around 150ml/5fl oz of boiling water. Bring the apricots to the boil and simmer for 40 minutes, or until the apricots have plumped up. Top up the water if you see it evaporating too quickly.
Soak the gelatine leaves in a bowl of cold water for five minutes, or until softened. Take the apricots off the heat and add the amaretto, to taste, before adding the gelatine leaves. Stir until dissolved.
Place the mixture into a food processor and blend to a purée. Set aside.
For the shortbread, preheat the oven to 190C/170C(fan)/Gas 5 and grease and line a 15cm/6in square tin with baking paper.
In a free-standing mixer with the beater attachment, cream together the butter (or margarine), sugar, ground almonds and almond extract until light and fluffy. Add the flour and beat until it just begins to clump together – don’t overbeat.
Bring the dough together using your hands and press into the tin so that it’s flat and even. Prick the dough with a fork and bake in the middle of the oven for 15-20 minutes. Remove from the tin, peel off the baking paper and cool on a wire rack.
Once the shortbread has cooled sufficiently (around 20-30 minutes), pour the preserve on top and smooth so that it evenly coats the shortbread and then put in the fridge to set for around 20-30 minutes.
For the marzipan, mix the sugar and almonds together in a bowl before adding the lemon juice, egg and almond extract. Mix together using a knife, using your hands towards the end to create a ball. Knead on a work surface until smooth, using a little icing sugar to stop the marzipan from sticking. Wrap in cling film and chill until needed.
To make the ganache, break the chocolate into squares and place in a bowl. Bring the cream and liquid glucose to just below boiling point and then pour it over the chocolate. Stir with a spatula until smooth and glossy. Cool at room temperature until needed.
Roll out the marzipan to a 3-5mm thickness and place on top of the shortbread. (The preserve should be sticky enough to hold the marzipan in place.) Put back into the fridge to set for 10 minutes.
Spread the ganache on top of the marzipan, ensuring it’s as even and smooth as possible. Chill in the fridge for at least 20 minutes.
To make the chocolate decorations, place the chocolate in a bowl over a pan of simmering water, making sure the water does not touch the bottom of the bowl. When the chocolate looks nearly melted but there are still a few bits of unmelted chocolate on top, remove from the pan and stir the chocolate gently until smooth. It should have thickened slightly. It's now ready to use. Line a baking tray with non-stick baking parchment.
Transfer the chocolate into a small piping bag and snip off a very small hole at the bottom. Pipe 4 x 3cm/1½in parallel lines close together onto the lined baking tray. Pipe another four lines across these to create a lattice shape. Repeat to create twelve lattice shapes. Leave to set slightly.
Using a 2cm/¾in round cutter, cut out 12 circles from the chocolate lattice decorations, leaving them on the baking tray to set completely before using.
When the millionaire’s shortbread is set, use a long and very sharp knife to cut the biscuit into 12 squares. Neatly sprinkle popping candy onto one side of the squares.
Carefully remove the small rounds of chocolate lattices from the paper and brush a small amount of gold leaf onto each of them (if using).
Carefully place a disk onto every square, the opposite side to the popping candy and present on a tiered cake stand.