Slice French bread into ½-inch thick round croutons and set aside. Grease a 9" x 13" baking dish with nonstick cooking spray. Set aside. In a large mixing bowl, whisk together eggs and egg yolks then set aside. In a large saucepan over medium-high heat, combine cream, milk, vanilla and sugar. Bring mixture to a low simmer then add white chocolate. Whisk until chocolate is completely melted. Remove pot from heat and quickly stir in whisked eggs. Blend thoroughly to keep eggs from scrambling. Set custard aside. Press one layer of French bread slices into the bottom of pan, making sure to fill all void spaces. Sprinkle with blueberries then ladle in ⅓ of custard mixture. Carefully press the custard into bread using the tips of your fingers. Continue to layer until all bread, blueberries and custard are used up. Sprinkle casserole evenly with cinnamon and nutmeg then top with butter. Cover dish with foil and let soak in a refrigerator a minimum of 5 hours prior to baking. This casserole is always best if allowed to set in refrigerator overnight before cooking. When ready to cook, preheat oven to 300°F. Bake covered approximately 1½ hours. Remove foil and bake 10–15 additional minutes or until top is golden brown. Serve hot with maple syrup or your favorite blueberry sauce. NOTE: This breakfast dish is best chilled in refrigerator overnight then cut into squares and heated in individual portions in microwave.