Preheat oven to 350°F. Combine first 3 ingredients; stir to blend.
Divide batter between 2 well-greased 8 or 9-inch round cake pans. Bake for 20-25 minutes or until set.
Cool completely. Invert one cake onto a serving plate; brush with half of liqueur.
In large bowl, whip next 5 ingredients at medium-high speed until fluffy. Spread half of whipped cream mixture onto cake. Invert second cake on top; brush with remaining liqueur and top with remaining whipped cream mixture.
Garnish with chopped mints. Chill 3 hours or more, until ready to serve.