Line the base and sides of a 20 cm cake tin with greaseproof paper - use oil to stick as butter will chill too much and make removing the pie difficult.
Place the mini eggs into a food processor and blitz to break up. Add the dark chocolate and blitz again then drizzle in the melted butter. Transfer the mixture to a large bowl then add the shredded wheat and mix everything together. Press the mixture into the cake tin, and push down evenly with the back of a spoon until the bottom and sides are completely covered- come right the way up to the top of the tin. Set aside to chill in the fridge.
To make the cheesecake filling, combine the cream cheese, mascarpone and sugar in a large bowl and then add the double cream, whisking until slightly thickened. Add the melted white chocolate and vanilla extract and stir to combine then spoon into the cake crust. Spread the mixture out and smooth the top with a palette knife or the back of a spoon, then place into the fridge for at least 3 hours, or until set.
To make the glaze, place the chocolate, butter, and cream in a heatproof bowl and place over a bowl of simmering water. Stir occasionally until melted then remove from the heat and allow to cool slightly. Pour the chocolate glaze over the cheesecake, spreading it out to the sides. Chill just until the chocolate has just set - about 10 minutes
To decorate, cover the whole cheesecake with mini eggs and serve in slices.