Dissolve the coffee in the boiling water. Put the egg yolks, sugar and liquid glucose in a large bowl set over a saucepan of simmering water and whisk for 5–10 minutes until very thick and the mixture leaves a trail when the whisk is lifted. Take the bowl off the heat and stand in cold water, then whisk until cool. Whip the cream in a second bowl until it forms soft swirls. Fold into the whisked yolks with the dissolved coffee.
Line a 20 cm (8 inch) shallow square cake tin with clingfilm, covering the inside of the tin completely. Pour in the coffee mixture and freeze for 3 hours until firm.
Melt the chocolate (see
Lift out the coffee ice using the clingfilm. Cut the ice into 3 even-sized strips, then cut each strip into 4 rectangles. Cut the chocolate into slightly larger pieces, then lift off the paper with a palette knife.
Layer 3 chocolate rectangles with 2 rectangles of coffee ice in between to make 6 stacks. Put one stack on each serving plate, then drizzle the liqueur around the plate. Serve at once.