Cake: Place cake mix, water, eggs and oil in mixer bowl. Using a paddle, mix on low speed 30 seconds.
Scrape bowl and paddle. Mix on low speed 30 seconds.
Scale batter into prepared (lightly greased or paper-lined) 16x12x1-inch half sheet pan. For standard oven, bake at 350°F 30-35 minutes; for convection oven, bake at 300°F 20-25 minutes.
Cool completely. Cut into 2 inch rounds.
Dark Chocolate Mousse: Bring cream just to a boil and pour over chocolate chips. Using a whisk, mix gently until chocolate is melted and mixture is smooth.
Cool completely. Gently blend in whipped cream in two stages. Blend one-third of the whipped cream into the chocolate mixture to lighten; then gently fold in the remaining whipped cream.
White Chocolate Mousse: Bring cream just to a boil and pour over white chocolate chips. Using a whisk, mix gently until chocolate is melted and mixture is smooth.
Cool completely. Gently blend in whipped cream in two stages. Blend one-third of the whipped cream into the chocolate mixture to lighten; then gently fold in the remaining whipped cream.
To Assemble: Pipe white chocolate mousse into the base of a shot glass, top with chocolate cake round and cherries; alternate with dark chocolate mousse until glass is full.
Top with white chocolate mousse and garnish with chocolate scroll.