Preheat oven to
180º C. Grease a baking dish. Melt the cooking chocolate in a double boiler.
Take condensed milk
in a mixing bowl, add castor sugar and beat with an electric beater.
Add butter to the
melted chocolate and mix well. Add this mixture to the condensed milk mixture and mix well.
Sieve flour, baking
powder and cocoa powder into this liquid mixture and mix in the cut and fold method till all the ingredients are well incorporated.
Add milk and most of
the walnuts in this mixture and mix. Transfer this mixture into a baking dish and top it up with the remaining walnuts.
Keep the dish in the
preheated oven and bake for 20-25 minutes.
Take the dish out and
let it cool a little before demoulding. Cut into squares, arrange them on a serving platter and serve.