Prepare and bake cake according to package directions, using two greased 9-in. round baking pans. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a bowl, whisk milk and pudding mix for 2 minutes. Let stand for 2 minutes or until soft-set. Stir in macaroons. Cut each cake horizontally in half. Place one bottom layer on a serving plate; spread with half of pudding mixture. Top with another cake layer; spread with jelly. Top with another cake; spread with remaining pudding mixture. Top with remaining cake.
In a small bowl, beat cream until it begins to thicken. Add sugar and vanilla; beat until stiff peaks form. Frost top and sides of cake. Refrigerate until serving.