Heavenly chocolate brownies

Recipe
200g dark chocolate
250g butter
1 3/4 cups brown sugar
4 eggs
1/2 cup cocoa powder
1 cup plain flour
1/4 tsp baking powder
optional: 1 cup chopped walnuts

1. Heat oven to 160C
2. Melt chocolate and butter in a saucepan over low heat, stirring until combined.
3. In a bowl place mix sugar, eggs, cocoa, flour and baking powder.
4. Add the chocolate mixture, mix until combined.
5. Pour into 23cm square lined tin.
6. Bake for 35mins, until set.
7. Cool in tin.