Peanut Butter-Banana Frozen Yogurt Cake

Preheat oven to 350 degrees F. Coat a 9-by-5-inch loaf pan with cooking spray. Line the bottom with parchment paper and coat the paper with cooking spray.
To prepare cake: Process freeze-dried banana in a food processor until powdered. Sift all-purpose flour, whole-wheat flour, baking powder, baking soda and salt together into a medium bowl. Stir in the powdered banana.
Whisk water, oil, sugar, vinegar and 2 teaspoons vanilla in a medium bowl. Add the wet ingredients to the dry ingredients and stir gently to combine, being careful not to overmix. Spoon the batter evenly into the prepared pan and smooth the top.
Bake the cake until a toothpick inserted in the center comes out clean, about 45 minutes. Let cool in the pan for 10 minutes, then turn out onto a wire rack. Remove the parchment and let cool completely, about 1 hour.
Meanwhile, to prepare banana whip: Pulse frozen banana chunks in a food processor for a few minutes, scraping down the sides as necessary, until reduced to small pieces. Add vanilla and 1 teaspoon honey; process until it’s the consistency of soft-serve ice cream. Spoon the banana whip into a freezer-safe container and freeze for at least 2 hours.
To assemble cake: Let the banana whip and frozen yogurt soften at room temperature for 10 minutes.
Meanwhile, using a serrated knife, cut a 1/2-inch layer off the top of the cake. Cut the remaining cake in half horizontally into 2 equal pieces (about 1 1/2 inches thick each). Line the loaf pan with parchment paper and place the bottom layer of cake into the pan.
Mash the frozen yogurt in a medium bowl with a fork. Swirl in the remaining 2 tablespoons honey. Spread the frozen yogurt mixture evenly onto the bottom layer of cake. Top with the middle layer of cake, then spread the softened banana whip evenly over that layer. Place the thin cake layer on the banana whip. Cover tightly with plastic wrap and freeze for at least 2 hours.
Meanwhile, to prepare ganache: Place white chocolate in the top of a double boiler over hot, not boiling, water. Whisk until completely smooth. Remove the top pan from the double boiler. Stir yogurt and peanut butter into the chocolate until smooth. Let cool completely, about 10 minutes.
To serve, spread the peanut butter ganache evenly over the top of the cake with an offset spatula. Sprinkle with peanuts, if desired. Cover and freeze until set, about 1 hour.