What additional item can be added to the Boulon Plateau Royal for an extra charge?

The Boulon Plateau Royal is likely a seafood platter or a sharing dish that includes a variety of high-quality seafood or delicacies. Adding caviar to this dish would elevate the overall experience, as caviar is considered a luxurious and gourmet item that complements seafood beautifully. The richness and unique flavor of caviar can enhance the flavors of the seafood already present on the platter, making it an excellent choice for customers looking to indulge.

In contrast, while options such as a glass of champagne, a side salad, or a crusty bread roll may be appealing additions to a meal, they do not carry the same level of luxury or exclusivity as caviar. Champagne, though classic, is typically a beverage choice rather than an enhancement to the dish itself. A side salad or bread roll might complement the meal but would not significantly elevate the experience in the way that caviar would. Therefore, caviar stands out as the most suitable choice for enhancing the Boulon Plateau Royal for an extra charge.