1/4 teaspoon baking soda
2 tablespoons vegetable oil
1 cup white sugar
1/4 cup cocoa powder
1 cup milk
1/4 cup butter
1 cup all-purpose flour
1 pinch salt
1 teaspoon vanilla extract
1/2 cup packed light brown sugar
In a large bowl, mix baking soda and oil. Stir sugar, cocoa, milk, butter and flour. Mix evenly and refrigerate for at least 1 hour.
Preheat oven to 350 degrees F (175 degrees C).
Pour mixture into a 9x13 inch pan. Bake in preheated oven for 1 hour. Remove from oven and cool completely.
While the chocolate is cooling, in a large bowl, combine brown sugar and vanilla extract. Mix thoroughly. Refrigerate until chocolate is firm.