Scoop out the Passion Fruit Pulp from the fruits (see note 2) and place it in a small saucepan with the Sugar and Vanilla. Mix to combine then turn on low heat and bring to a simmer.
In the meantime, mix the Gelatine powder with about 1 tablespoon of cold water in a small bowl. Leave for a couple of minutes or until it turns into a thick paste.
Remove the passion fruit mixture from the heat and whisk in the bloomed gelatine. Mix well until the gelatine has fully dissolved.
Transfer into a clean bowl, cover with plastic wrap touching the surface of the mixture and place in the fridge for 30 minutes to 1 hour (see note 3).
Place the cold Heavy / Thickened Cream in a large mixing bowl or the bowl of your stand mixer. Whip on medium speed until you reach medium peaks. Add the passion fruit mixture and continue to whip on medium low speed. Stop just before you reach stiff peaks. The mousse should still feel slightly loose and fluid (see note 4).
Scoop it into individual serving cups and place in the fridge to set for at least 3 hours, preferably overnight.
Passion Fruit Curd Topping
Place the Passion Fruit Pulp and Lemon Juice in a small saucepan and turn on medium low heat. Bring to a simmer.
In the meantime in a separate heat-proof bowl, whisk together the egg yolks and sugar. Slowly pour the passion fruit mixture over the eggs while whisking, mix well then pour it all back into the saucepan. Place on low heat and cook for about 2 to 3 minutes or until the sugar has melted and the mixture has very slightly thickened.
Add the butter a little bit at the time, stirring well until fully incorporated before adding more.
Continue to cook on low heat for about 10 minutes or until the curd has thickened (see note 5).
Leave to cool down for about 30 minutes then transfer into a clean jar. Place in the fridge to chill until it feels cool to the touch.
Pour a little bit of the curd over the set mousse cups and gently spread it around. Keep in the fridge until ready to serve.
Notes
This recipe will yield 4 large or 6 small cups.
Passion fruit pulp: You can use both fresh and frozen passion fruit pulp (thawed) for this recipe. This contains both the seeds, juice and flesh of the passion fruit. I don't recommend using canned passion fruit that is usually preserve in syrup.
To make this recipe without the passion fruit seeds, pour the pulp through a thin mesh sieve first. Note that you will need the same amount of passion fruit juice than of passion fruit pulp, so make sure to account for extra passion fruits.
It could take more or less than 1 hour depending on the container it is stored in, but make sure it doesn't feel warm to the touch before using. To cool it down more quickly, chill it inside a large shallow pan such as a brownie pan instead of in a bowl.
Alternatively, you can whip the cream until you get stiff peaks, then gently fold in the passion fruit mixture with a spatula until fully incorporated.
The curd should coat the back of a spoon or spatula without dripping when it is fully cooked. It should have reached about 82 degree celsius when it is ready.