1Heat oven to 325°F. Generously grease and lightly flour shaped (12-cup) Bundt® pan and bottom of Bundt® Tunnel Insert, or spray with baking spray with flour. Spoon almonds into bottom of pan.
2In large bowl, beat cake mix, water, oil and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour over almonds in pan. Place tunnel insert on center of Bundt pan.
3Bake 38 to 44 minutes or until toothpick inserted toward center comes out clean. Using sharp or serrated knife, immediately cut off excess cake across top of Bundt and tunnel insert pans. Carefully loosen tunnel insert; remove. Cool cake in pan 10 minutes; remove from pan to cooling rack, placing cake tunnel side down. Cool completely, about 1 hour.
4Make pudding mix as directed on box for pudding--except use 1 1/2 cups milk. When pudding is boiling, remove from heat. Stir in chopped white chocolate baking bars until melted. Stir in almond extract. Refrigerate about 15 minutes or until mousse is set. When cake is cool, turn cake over and spoon mousse into tunnel. Place cake filled side down on serving plate. Sprinkle with powdered sugar if desired. Stored covered in refrigerator.