Grease an eight-inch round microwave dish. Melt chocolate and butter in a microwave bowl for one minute on Microwave HIGH (100%).
In another bowl sift flour and baking powder. Mix the melted chocolate and butter well. Add powdered sugar, vanilla essence and mix.
Add the flour and mix. Correct the consistency by adding milk. Add walnut kernels and mix gently.
Transfer the mixture into the prepared microwave dish. Cook for seven minutes on Microwave HIGH (100%) Allow standing time of five minutes.
Cool, slice and serve.
Makes one (500 g) 8-inch cake