Heat oven to 180°C. Spray three 23cm round pans with cooking spray. Line bottom of pans with cooking parchment paper rounds; spray with cooking spray.
Make cake as directed on box and pour evenly into pans.
Bake 35 to 40 minutes or until cake tester or toothpick inserted in center comes out clean and cake top is no longer wobbly. Cool on wire racks, about 10 minutes. Invert cake layers onto wire racks and remove parchment paper. Cool completely, about 1 hour.
In large bowl, place chopped chocolate and set aside. In 4-liter saucepan, heat whipping cream and honey to a simmer over medium heat. Remove from heat and add 2 teaspoons vanilla. Pour mixture over chocolate and cover bowl with plastic wrap; let stand 5 minutes. Remove plastic wrap and beat with wire whisk until chocolate is smooth. Cover bowl with plastic wrap and chill 30 minutes. Stir well and refrigerate 30 minutes longer. Continue to stir every 30 minutes until icing is spreadable, about 2 hours total.
Place 1 cake layer on plate and spread approximately 340 grams icing to edge of layer. Top with another layer and spread 340 grams icing to edge. Top with last layer. Frost side and top with remaining icing. Smooth top and side of cake. Use hands to liberally press crushed cookies all around cake.