Coffee & Croissant
The only other thing you need with your croissant is a large cup of coffee in which to quickly dunk it. Where extra butter adds a new layer of luxurious creaminess, coffee offers an earthy, complimentary bitter contrast while intensifying the sweetness of the croissant. It gives the croissant a new, deeper resonance. Alternate the two (buttered chunk, then dunk) and a croissant becomes a true breakfast classic.
As for adding savoury toppings and fillings to this stridently sweet pastry, that is strictly interdit. How to Eat would not be so rash as to say you should never cross the sweet ’n’ savoury streams, but it in this context it is infantile. Why in the name of all that is holy would you want sausages, ham, bacon or gruyère, scrambled eggs or goat’s cheese served on a sugary croissant? Moreover, if you did want that effect, why not use one of the many bizarrely sweet continental sandwich breads that have the marginal advantage of being square.
Coffee. Hot chocolate is a vile concoction. No other drinks are even in the running.