Crush biscuits either in food processor or plastic bag with rolling pin
Melt butter
Stir in biscuits
Press into tin and chill
Chop white chocolate and melt
Place cream, crème fraiche and liqueur into large mixing bowl and beat using hand mixer
Mixture should forms soft peaks
Fold in melted chocolate
Pour over biscuit base and chill for at least 4 hours, overnight is ideal
Serve dusted with sieved cocoa