Crush the biscuits in a blender or food processor until dust. Add in the butter and mix well with your hands. Put into 3 mini tart pans and place in the freezer while preparing the rest of the recipe.
In a bowl whisk the eggs with the sugar for 3-5 minutes. Add the lime juice and zest, mix and set aside.
In a saucepan over the lowest heat possible, melt the gelatine in the milk, stirring constantly. Slowly pour in the eggs preparation and add the corn starch (slowly as well), never stopping to stir. You will know when to stop when the liquid thickens (5 to 10 minutes). Remove from heat and let cool for about 10 minutes.
Open the passion fruits in half, spoon out the pulp and add to the preparation, mixing just until incorporated.
Remove the tartlets bases from the freezer and pour in the preparation.
Refrigerate for at least 2 hours, sprinkle with lime zest and serve.