Blend brown sugar, flour and butter. Set aside 1 cup of mixture to be mixed later with nuts and Heath Bars.
Add baking soda, salt, egg, milk and vanilla extract and beat.
Pour into a greased 13 x 9-inch cake pan.
Combine 1 cup mixture that was set aside, nuts and Heath Bars. Sprinkle over cake.
Bake at 350 degrees F for 35 minutes.