In a saucepan combine the water, Xylitol and butter, Bring to a boil, stir frequently and continue cooking for 7-9 minutes, until 1.2 of the water evaporated and the mixture thickens.
Whisk together the eggs and egg yolks. Combine the sweetener and heavy cream, vanilla extract and pinch of salt and whisk to combine. Add the eggs and whisk until incorporated.
Strain the mixture into the ramekins.
Place ramekins in a larger baking dish and pour hot water inside the dish, covering the ramekins half way through.