Heat oven to 200C/180C fan/gas 6.
Grease the base and sides of a deep
20 x 30cm tin. Unroll the pastry sheet
and use it to line the tin, pressing into
the base and sides. Line with baking
parchment and baking beans, then bake
blind for 15 mins. Remove the paper and
beans, then bake for 5 mins more.
Reduce oven to 180C/160C fan/gas 4.
Meanwhile, put the gooseberries in a
pan with the elderflower cordial, if using,
and 3 tbsp water. If you’re not using the
cordial, use 6 tbsp water. Cover and cook
for 5 mins until the berries start to break
down. Mix the cornflour and sugar
together, then add to the gooseberry
mixture and stir continuously until
thickened. Spread evenly over the pastry.
Put all the ingredients for the sponge
in a large bowl and beat with an electric
whisk until smooth. Spread evenly over
the gooseberry mixture and bake for
25 mins until golden and firm to the
touch. Cool in the tin.
To decorate, mix the icing sugar with the
cordial or water to make a smooth icing.
Drizzle over the cake and scatter over the
nuts. Leave until set, then cut into fingers.