Preheat the oven to 200C/400F/Gas 6. Grease and line a 33 x 23cm/13 x 9in Swiss roll tin with baking parchment.
Crush the cardamom seeds in a pestle and mortar until almost powder.
For the Swiss roll, whisk the eggs and sugar in a bowl until the mixture becomes light and when you remove the whisk from the bowl it leaves a trail - this could take 10-15 minutes.
Add the ground cardamom seeds to the egg mixture. Sieve the flour into the egg mixture and carefully fold it in. Pour the mixture into the tin and give it a shake to level it, so that it spreads evenly.
Bake for 8-10 minutes, or until the cake turns golden-brown.
Tip the cake out onto a sheet of baking parchment sprinkled with caster sugar. Roll it and cover with a clean tea towel. Allow it to cool, rolled up.
While the cake is cooling, prepare the filling. Pour the cream into a large bowl and add the sugar. Whisk until soft peaks form when the whisk is removed from the bowl. Add the coffee to this mixture and mix well.
Melt the chocolate in a bowl and cool it down slightly. Pour the chocolate into a piping bag and make flower patterns on an acetate sheet (or you can make any other design you like). Put this sheet in the fridge until the chocolate is set. Once set, you can peel the flowers off the sheet.
Once the cake has cooled, unroll it. Spread almost all the coffee cream evenly over the cake, and sprinkle the pistachios over it. Once again roll the cake neatly and decorate with some more coffee cream and sprinkle over some nuts. Finally place few chocolate flowers on top. Dust with icing sugar.