Heat oven to 180C/160C fan/gas 4.
Lightly grease and line the base of
2 x 20cm sandwich tins with baking
parchment. Grease the tins again,
dust with a little caster sugar and a
little flour, then tap out any excess.
Put the eggs and sugar in a heatproof
bowl and, using an electric whisk, mix
briefly to combine. Place the bowl over
a pan of steaming water and continue to
whisk until the mixture is pale and thick
– when the whisk is lifted, the mixture
should leave a trail on the surface lasting
about 5 secs. Remove the bowl from the
pan and continue beating for 2 mins.
Continue to whisk the mixture while
trickling the melted butter around the
edge of the bowl. Sift in the flour and
ground pistachios, very gently give the
mixture 2-3 folds, then add the blueberries
and fold again, being careful not to knock
out all the air. Divide the mixture between
the tins and bake for 25-30 mins, until a
skewer inserted comes out clean.
To make the filling, beat the butter and
sugar together until pale and fluffy. Add
the cardamom, then drizzle in the cream.
Continue to beat until light and airy.
Cool cakes in their tins for 10 mins, then
turn out onto a wire rack. Remove lining
paper when completely cooled. Sandwich
the cakes together with the cardamom
cream, top with some more, then
decorate with pistachios and blueberries.