1/2 cup butter
3 tablespoons brown sugar
1 1/2 cups packed light brown sugar
1 cup all-purpose flour
1 teaspoon baking powder
1 teaspoon baking soda
2 eggs
2 teaspoons vanilla extract
3 cups semisweet chocolate chips
1 tablespoon light whipping cream
1 1/2 teaspoons milk
1 cup confectioners' sugar for decoration
Preheat the oven to 350 degrees F (175 degrees C).
In a medium bowl, cream together the butter and brown sugar until light and fluffy. Beat in the flour, baking powder and baking soda. Stir in the eggs, one at a time, beating well after each addition. Mix in the chocolate chips and vanilla. Combine the chocolate and flour mixture, and mix into the cream mixture along with the milk. Pour into the prepared crust.
Bake in the preheated oven for 40 minutes, until a toothpick inserted into the center of the chocolate bars comes out clean. Carefully remove from the oven and place onto a wire rack. Chill for at least one hour, then remove from pan and cool completely.