Cut the butter into a small dice.
Keep the eggs at room temperature.
Peel, core and dice the apples. Place the apples in a pot and cook over a slow heat along with the calvados until the apples become pureed. Add the sugar and keep cooking until the sauce thickens. Off the heat gradually whisk in the butter and then the eggs. In a blender blitz the mixtureuntil it becomes a smooth paste. Pass through a sieve and immediately pour into warm, sterilised jars and seal.
«Use within 4 weeks. Once opened, store in the fridge. »