Cake:
1-1/2 cups all-purpose flour
1 cup granulated sugar
1/4 cup unsweetened cocoa powder
1 tsp. baking powder
1 tsp. baking soda
1/2 tsp. salt
1/3 cup butter, melted
1 tbsp vinegar
1 tsp. vanilla
1 cup warm water
Brown Sugar Frosting:
1-1/4 cups lightly packed brown sugar
1/3 cup light cream
1/4 cup butter
1-1/2 cups (approx) sifted icing sugar
Cake: In 8-inch square cake pan, combine flour, sugar, cocoa, baking powder, soda and salt; stir well to blend. Make 3 wells equally spaced in dry mixture. Pour melted butter into one hole, vinegar into another and vanilla into the third. Pour warm water over top. stir well with fork until smooth.
Bake in 350° F oven for 35 to 40 minutes or until tester inserted in centre comes out clean. Let cool in pan.
Brown Sugar Frosting: In small saucepan, combine brown sugar, cream and butter. Bring to boil, stirring to melt butter; boil gently for 2 minutes, stirring constantly. Remove from heat; let cool to lukewarm. With electric mixer or by hand, gradually beat in enough icing sugar to make a good spreading consistency. ( You may need to add up to 1/2 cup more icing sugar if using electric mixer.) Spread immediately over cake. Sprinkle wit walnuts if desired.