Spray a 11 x 17" jelly roll pan with PAM. Mix the cake mixture for 6 - 8 minutes. Layer 1/2 of the batter then half of the brown sugar mixture; then batter and top with remainder of the brown sugar mixture. Bake at 350 degrees for 20 - 30 minutes.
Glaze (optional); 1 1/2 cups powdered sugar, 9 tsp. milk and 1/2 tsp. each vanilla and butter flavoring. Drizzle over warm cake. This is good without the glaze so it is your preference on whether to glaze it or not. This makes approximately 60 bars.