Boil potatoes until cooked, drain and allow to dry.
Pass the potato through a mouli or fine sieve and set aside.
Separately, pass the avocado through a mouli or fine sieve and set aside.
Bring cream & butter to boil and divide the cream into ¾ and ¼ quantities.
Add all of the potato to the ¾ of cream and season.
Add the avocado to the remaining cream and season.
Serve both types of mash folded together