Melt the butter fully.
Add in xanthan gum, swerve and salt. Mix in and add one more teaspoon of xanthan gum if not thick enough.
Slowly add in the heavy cream then water.
Raise heat to boil.
Blend the yolks and slowly add in the hot milk.
Put back on the fire to cook for 2 minutes while mixing the whole time.
Let cool and pour in vanilla.