Line a 9" round layer cake pan with aluminum foil. In large mixing bowl, combine sweetened condensed milk, peppermint extract & food coloring. Fold in whipped cream. Pour into prepared pan; cover. Freeze at least 6 hours or until firm.
Meanwhile, prepare and bake cake as package directs for two 9" round layers. Remove from pans; cool completely.
With fork, poke holes in cake layers, 1" apart, halfway through each layer. Spoon small amounts of liqueur into holes. Place one cake layer on serving plate; top with frozen mixture, then second cake layer. Trim frozen layer to edge of cake layers.
Frost quickly with whipped topping. Return to freezer at least 6 hours before serving. Garnish as desired.