Preheat oven to 350°F. Melt 3 sticks of butter in a small saucepan over medium-low heat. Remove from heat and stir in sugar. Stir chocolate into butter mixture until melted. Cool slightly.
Using an electric mixer, blend eggs, vanilla extract, cornmeal, and five-spice powder in a large mixing bowl on medium speed until well combined – approximately 2 minutes. Add chocolate mixture and blend well – approximately 1 minute.
Melt remaining 2 sticks of butter over low heat in a small saucepan. Combine cake mix and melted butter in a bowl and mix well on medium-low speed – approximately 2 minutes.
Press mixture into the bottom of a 10 x 15-inch jellyroll pan.
Pour chocolate mixture over the cake mix crust and bake until set – 30-35 minutes. It will be firm and will spring back slightly when touched.
Cool to room temperature, and then dust with powdered sugar.
Cut into approximately 3 x 2-inch bars.
Feel free to freeze any of the extra bars that you may not need immediately.