Prepare cake mix according to manufacturer’s directions. Deposit 12 oz. of batter onto a half sheet tray lined with a silpat (parchment paper will wrinkle and may break the small, smooth cake layers). Spread in an even layer, all the way to the edges of the pan. Bake at 350 until light golden brown, about 10 minutes depending on oven. Cool cakes completely. Melt chocolate and mix in flavoring and coloring to taste. Spread one side of the cake with 8oz melted chocolate, being careful to keep it in an even layer. Place a clean silpat on top of the spread chocolate and flip cake over. Spread an additional cup of chocolate on top layer, sprinkle with candied citrus peels and let set up at room temperature.
To make your own candied citrus peel: peel desired citrus fruit with sharp peeler. Remove any extra pith with a paring knife and slice peel to very thin strips. Blanch strips in boiling water 3 times, being sure to shock in ice water in between. Using a 1:1 ratio simple syrup, bring syrup to a boil, add peels, and poach, using parchment to cover the surface of the pot until peels are translucent. Remove from heat, drain (save the syrup and use it for another purpose), roll in granulated sugar and leave on a parchment lined sheet tray to dry overnight. Peel is ready the next day and should be stored in an airtight container.