Preheat the oven to 190°C.
Grease and line a 23cm deep cake tin.
Whisk the butter and sugar until light and fluffy.
Add the eggs individually, beating well between each addition.
Mix in the coffee and ground cardamom, then fold in the flour.
Bake the mixture in the tin for 20-25 minutes until golden and allow to cool.
Whisk the double cream into soft peaks.
Gently whisk in the icing sugar, cardamom seeds, and pistachios until firm peaks form.
Mix the remaining icing sugar and warm coffee until smooth.
Halve the cake, spread pistachio cream on the base, top with the other half, and drizzle with icing.
Cut the cake into wedges and serve.