Preheat the oven to 160°C/fan 140°C, grease a 24cm spring-form tin and line with baking paper
Mix the crumbs and butter and press in an even layer over the bottom of the tin. Add 25g of the Easter egg, broken into pieces, across the surface. Chill for 15 minutes
Use an electric hand mixer to beat the cream cheese, yogurt and fromage frais until smooth. Add the caster sugar, and beat for 3 minutes until mixed, then beat in the cornflour and the eggs, a little at a time
Pour into the tin and put on a baking sheet in the middle of the oven and bake for 55-60 minutes. The cake should have a wobble in the centre. Turn the oven off and, leaving the door slightly ajar, let the cake cool completely (about 3 hours)
Remove from the tin, and decorate with the remaining Easter eggs whole and grated to serve.