The ganache took a little experimenting - it's essentially a white chocolate ganache with irish cream in it, but I wanted to put as much irish cream in to have an intense flavour but still have the right consistency.
For the shells,
110g ground almonds200g icing sugar
50g caster sugar
90g egg whites
colouring of your choice
Whisk egg white to stiff peaks, gradually adding the caster sugar. Add colouring to achieve intensity you desire.
Fold almonds and icing sugar into the eggwhites, "macaroning" until you achieve the correct consistency.
Pipe rounds onto baking trays and leave until a skin forms (usually at least 30 mins, much longer if humidity is high).
Bake at 150 deg C for 12-13 mins, cool and remove from trays. Brush with edible shimmer dust if desired.
For the ganache,
100g white chocolate
35g irish cream liquor
Heat cream and irish cream until almost to the boil. Add white chocolate and mix until smooth. Set aside until cooled and thickened.