Step 1If cream cheese frosting has been chilled, place within the massive bowl of stand mixer fitted with the paddle attachment. Beat on medium-high velocity till easy and pliable, about 30 seconds.
Step 2Switch 1 1/2 cups frosting to a piping bag fitted with a 1″ spherical tip. Set remaining frosting apart.
Step 3If caramel sauce is chilly and stiff, warmth within the microwave in 15-second increments till easy and pourable.
Step 4Utilizing a serrated knife, degree tops of cooled truffles. Discard (or eat!) trimmings.
Step 5Place 1 cake layer on a platter. Unfold prime with an excellent layer of frosting (about 3/4 cup). Pipe a hoop of frosting round fringe of cake, then pipe one other ring of frosting immediately on prime of that ring, making a tall dam to carry the fillings in. Fill with 1 cup apple filling. Sprinkle with 1/2 cup crumble. Drizzle crumble with 2 tablespoons caramel.
Step 6Place one other cake layer on prime. Unfold prime with an excellent layer of frosting. Pipe a double-stacked ring of frosting round fringe of second layer as earlier than. Fill with 1 cup apple filling, 1/2 cup crumble, and a couple of tablespoons caramel. Place third cake layer on prime easy facet up.
Step 7Frost prime and sides of cake with a skinny coat of frosting, then refrigerate no less than 2 hours or as much as in a single day. Refrigerate remaining frosting.
Step 8When prepared to complete, stir remaining frosting till easy and pliable. Apply a clear layer of frosting over crumb coat. Drizzle with remaining 1/2 cup caramel, then prime with remaining crumble.
