100g egg whites
100g caster sugar
100g icing sugar
250g white chocolate, chopped
100g thickened cream
Green food colouring
Melted dark chocolate or black royal icing, for decorating
Preheat oven to 100C fan forced.
Place egg whites in the bowl of a stand mix with the whisk attachment and whisk to stiff peaks.
Mix the caster sugar and icing sugar together in a bowl and then with the mixer on medium speed, add the sugar 1 tablespoon at a time ensuring the mixture returned to stiff peaks after every addition. Continue until all the sugar is incorporated and then mix on high for another 3-5 minutes until the mixture isn't grainy when rubbed between your fingers. Transfer to a piping bag with a large round tip.
Pipe 16 round short bases and 16 tall ghost shapes onto a large lined baking sheet. Bake for 1 hour until crisp then turn the oven off and leave the meringues in there for another hour.
Cool completely then pipe faces on to the tall ghost meringues with a little melted dark chocolate (or black royal icing).
While the meringues are cooking and cooling, make the ganache filling. Place the white chocolate in a large glass bowl and set aside. In a microwave-safe bowl, heat the thickened cream in short 30-second bursts until the cream is bubbling at the edges, and then pour it onto the white chocolate. Allow the cream and chocolate mixture to sit for 2-3 minutes, then add green food colouring and mix until the white chocolate has melted and combined with the cream to form a ganache. Set aside the ganache at room temperature to cool and thicken.
Transfer the ganache to a refrigerator until chilled, then whip in a stand mixer (or with a hand mixer) until the mixture is fluffy and lighter in colour.
Pipe a round of ganache onto the base meringues and top with a tall ghost meringue. Serve.