Whisk the yolks and the zest of 2 of the limes (reserve the other last third of the zest for serving) well. You want to allow it to thicken and get some air in there.
Add the lime juice, condensed milk and whisk until well mixed. Whisk in half of the finger lime pulp (if using) (see notes) and reserve the rest for serving.
Pour the filling into the cooled crust and bake for 12 minutes, or until just set. The surface should look firm but not browned. Cool to room temperature.
Refrigerate for a minimum of 2-3 hours to chill. Note - This can be done up to five days in advance.
Whip cream to soft peaks, then gently fold in the sugar and vanilla.
Spoon the cream over the chilled pie (see note for other optiosn).
You could serve as is, with the remaining lime pulp or zest on top OR if time allows chill the pie again for another 2 hours, so that it slices more evenly.