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You can create even zig-zag lines by moving your arm back and forth in a uniform way across the entire sheet of cake balls. For decorating the cake pops, you can either sprinkle chopped chunks or use a food processor to create finely chopped pieces. You can also use other nuts, like peanuts, as a substitute if walnuts are unavailable. To ensure a hard coating and for any toppings to appear more uniform, place the cake balls in the freezer or refrigerator for about an hour or two.

Summary:
Drizzle additional melted chocolate on top. Sprinkle the walnuts on top. Chill the cake balls again. Finished.