Preheat oven to 350*. In a large mixing bowl stir together milk, eggs, syrup, brown sugar, and vanilla.
Spread bread cubes in an ungreased 3 qt. rectangular baking dish. Sprinkle with chopped semisweet and white chocolate.
Pour egg mixture evenly over bread.
Bake, uncovered, for 50 to 55 minutes or until pudding is puffy and knife inserted near center comes out clean. Cool slightly (pudding will fall in center). Drizzle with warm Bourbon Chocolate Sauce.
Bourbon Chocolate Sauce: In a heavy saucepan stir 4 ounces chopped semisweet chocolate over low heat just until melted. Stir in 2/3 cup whipping cream and 1/4 cup sugar.
Cook and stir over medium heat for 5 to 6 minutes or just until mixture begins to boil.
Remove from heat; whisk until smooth. Stir in 2 to 3 Tbsp. bourbon, if desired.C ool slightly before serving.