If it suits your schedule more, you can make ahead, cover and refrigerate after pouring the egg-milk custard mixture over the panettone. It can soak a few hours, then add the demerara sugar shortly before baking.
Calories: 631kcal | Carbohydrates: 61g | Protein: 12g | Fat: 39g | Saturated Fat: 23g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 10g | Trans Fat: 0.5g | Cholesterol: 240mg | Sodium: 390mg | Potassium: 383mg | Fiber: 2g | Sugar: 38g | Vitamin A: 1398IU | Vitamin C: 0.4mg | Calcium: 159mg | Iron: 1mg