Beat the yolks together with the brown sugar in a glass or metal bowl. Add the maple syrup, set over a water bath, and cook, whisking, until the mixture reaches custard consistency and coats a spoon, about 15 minutes. It should be quite thick. Remove from the heat and stir in gelatine. Set aside to cool completely. This is important: if warm it will deflate the egg whites.
When cool, beat the whites to peaks and beat the cream to peaks, separately. Fold them into the custard. Whip the cream to peaks and fold it in. Turn the mixture into a serving bowl. Cover, and chill for at least four hours before serving. Alternatively, pipe into parfait glasses and chill.