Set and oven to 175 *
Sift the flour into a bowl and mix with the ground almonds and caster sugar.
Add the whole eggs and whisk thoroughly to incorporate as much air as possible.
Melt the butter and coat some silicon baking paper, place on a baking tray.
Whisk the egg whites, at the same time gradually trickle in the sugar. When incorporated, continue to whisk to soft peaks.
It is very important that these are not over whisked as this will result in a tough sponge.
The egg yolks can be retained for the buttercream if necessary
Fold the two mixes together carefully and spread in a thin even layer over 3 lined trays.
Bake in the oven for 7 minutes, or until the sponge is firm and springey to touch
«This mix will make 3 sheets or alternatively 6 small individual Opera Gateau's. If the baked sponge is crispy, refrigerating for an hour will moisten it, as will leaving to soak in coffee syrup or Tia Maria!»