Lightly grease a 7-inch springform pan.
Crush the biscuits and Maltesers into fine crumbs (a food processor works well). Melt the butter and pour it over the crumbs. Mix until combined.
Press the mixture into the pan, using a glass or jar to smooth it out. Pop it into the fridge.
For the filling, melt the chocolate and dissolve the malted milk powder, then leave to cool.
Using an electric whisk, mix together the cream cheese, powdered sugar, malted milk powder, cocoa powder, and melted chocolate until smooth.
In a separate bowl, whip the heavy cream until thick and forming stiff peaks (be careful not to overwhip!).
Fold the whipped cream into the chocolate cream cheese mixture.
Spread the mixture evenly over the biscuit base and leave to set in the fridge overnight.
For the topping, heat the cream to boiling. Pour it over the chocolate to melt it. Let it sit for a few minutes, then mix to form a ganache. Leave it to cool.
Pour half of the ganache over the cheesecake. Cover with half of the crushed Maltesers, then pour over the remaining ganache. Finish by sprinkling the remaining crushed Maltesers on top.