Arrange a rack in center of oven; preheat to 350°. Grease a 13" x 9" baking pan with cooking spray. In a large bowl, make cake mix according to box directions. Pour batter into prepared pan.
Bake cake until a tester inserted into the center comes out clean, 20 to 25 minutes. Let cool 10 minutes.
Using a fork, poke cake all over. Brush 2 Tbsp. liqueur over top (if using). Let cool.
Cut about half of cake into ½" pieces; reserve remaining cake for another use.
In a medium bowl, whisk pudding mix and milk until starting to thicken. Refrigerate until ready to use.
In a large bowl, using a handheld mixer on medium-high speed, beat cream and confectioners’ sugar until medium peaks form.
In a small bowl, combine preserves and remaining 1 Tbsp. kirsch (if using).
In small glasses or jars, place 4 to 5 cake pieces to cover the bottom. Top with a layer of whipped cream, preserves mixture, then chocolate pudding. Repeat layers once more. Top with another spoonful of whipped cream and chocolate shavings. Refrigerate until ready to serve.
