The recipe I use is based on Pierre Herme's recipe which requires fresh passionfruit, juiced. The trick to getting lots of juice out of passionfruit is to blitz the pulp first then strain it. Another option is to buy frozen passion fruit juice (Boiron) but this can be quite costly.
For the shells
110g ground almonds
200g icing sugar
50g caster sugar
90g egg whites
food colouring - yellow and red
Whisk egg white to stiff peaks, gradually adding the caster sugar. Add colouring to achieve intensity you desire - I use yellow and a touch of red colouring.
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).
You can dust these with unsweetened cocoa powder if you like, or leave them plain.
For the passionfruit ganache
100g passionfruit juice (around 5-6 passionfruit)
40g good quality unsalted butter
140g milk chocolate (~40% cacao)
Heat passionfruit juice to around 60 degrees Celsius and put aside.
Melt chocolate and butter and add the passionfruit juice, whisking until completely combined.
This ganache takes longer to set than most and is best left in the fridge overnight.