Preheat the oven to 180 degrees Celsius or gas mark 4 and line a 20 x 20cm tin with baking paper.
Mix together the butter and sugar until smooth.
Add the eggs, vanilla essence, flour and cornflour and continue mixing.
Crush the mini eggs slightly (I bash the pack with a rolling pin), then fold in two-thirds of the pack into your mixture.
Pour the blondie mix into the tin and spread it with a spatula into all four corners.
Bake for 25 minutes or until a cake skewer comes out clean.
Top with the rest of the mini eggs (push some into the top of the blondie while it's soft) then leave to cool.
Cut into squares to serve.