Heat oven to 350°. Grease a 13 x 9 x 2-inch baking dish.
In a large bowl, beat eggs until foamy. Add cake meal, sugar, chocolate chips, oil, walnuts, potato starch and vanilla. Stir until well combined.
Spoon into baking dish and spread evenly. Sprinkle with 2 tbsp of the cinnamon sugar. Bake at 350° for 30 minutes.
Remove from oven and cool 15 minutes on a wire rack. Heat broiler.
Slice bread vertically into thirds, then slice each third horizontally into six 1-inch pieces. Place slices on their sides on a baking sheet. Sprinkle with half the remaining cinnamon sugar; broil 1 minute. Turn and sprinkle with remaining cinnamon sugar; broil 1 minute. Cool before serving.