Grease a square pan and preheat the oven to 160C.

Melt chocolate with butter in a hot water bath or microwave.

In a clean bowl beat the eggs with the sugar.

Add the flour, baking powder and essence.

Add crushed walnuts to the mixture. If the batter is too thick add a little milk and mix.

Pour into a buttered square mould(it should not be too thick). Bake for 10 to 15 minutes. Cool, cut into squares and serve.