Stir together coffee and 3/4 cup warm water until coffee is dissolved. Cool.
Cut cake into 14 slices. Cut each slice in half diagonally. Place triangles in bottom and up sides of a 9-inch deep-dish pieplate. Drizzle coffee mixture over cake.
Beat mascarpone cheese, sugar, and chocolate syrup at medium speed with an electric mixer until smooth. Add 2 1/2 cups whipped topping, and beat until light and fluffy.
Spread cheese mixture evenly over cake. Dollop remaining whipped topping around edges of pie. Sprinkle with candy. Chill 8 hours.