Crush the digestive biscuits into fine crumbs and mix with the melted butter until the mixture resembles wet sand.
Firmly press the biscuit mixture into the base of a lined 20–23cm springform tin and refrigerate for 20–30 minutes until firm.
Beat the softened cream cheese until completely smooth.
Add the icing sugar and vanilla extract, then mix until fully combined.
Fold in the melted and slightly cooled milk chocolate.
In a separate bowl, whip the double cream to soft peaks.
Gently fold the whipped cream into the chocolate mixture.
Fold in the crushed Maltesers, making sure they are evenly distributed.
Spoon the filling onto the chilled biscuit base and smooth the surface with a spatula.
Refrigerate for at least 6 hours or overnight until fully set.
Decorate with whole and crushed Maltesers, drizzle with melted chocolate if desired, slice, and serve chilled.