Process biscuits in a food processor to fine crumbs, transfer to a bowl.
Melt butter and add to biscuit crumbs, stir until well combined.
Use your fingertips to press crumbs into base of prepared pan. Refrigerate for 20 minutes.
Using an electric mixer, beat cream cheese, icing sugar and milk until smooth.
Boil water and place into a heatproof bowl/jug. Sprinkle gelatine over boiling water and stir vigorously.
While electric mixer is still mixing, pour gelatine mixture into cream cheese mixture and continue to have mixing for another minute. Set aside.
Pour thickened cream into a separate mixing bowl, and whip.
Melt dark chocolate and add half of cream cheese mixture to melted chocolate.
Fold half of the whipped cream into dark chocolate mixture.
Pour dark chocolate mixture over biscuit base and freeze for 10 minutes.
Melt white chocolate and add remainder of cream cheese mixture to melted chocolate.
Fold the remainder of the whipped cream into the white chocolate mixture.
Pour white chocolate mixture over dark. Cover. Refrigerate overnight.
Optional 1 – grate extra chocolate and sprinkle over top
Optional 2 – serve with berry coulis (2/3 cup sugar, 1 cup water, 3 ½ cups berries (Sara Lee frozen mixed berries); Boil water, add sugar to dissolve, Add berries, bring to boil, simmer for 15 minutes.