Brush the melted butter over the cut sides of the croissants, then sprinkle them with the sugar. Set aside.
Beat the chestnut purée with the mascarpone, yogurt and honey until smooth.
Heat a griddle pan over a low heat and cook the croissants gently, cut-side down, for 2–3 minutes until hot and golden.
Transfer the croissants to serving plates, top with some of the chestnut cream and drizzle with a little extra honey. Sprinkle with a few chopped marrons glacés or crushed chocolate coffee beans, if liked, and serve immediately.