Sprinkle gelatin over water in a small saucepan and let stand 1 minute to soften. Cook over low heat, stirring, until gelatin is dissolved, 1 to 2 minutes.
Remove from heat and whisk in 1 tablespoon passion-fruit nectar at a time until gelatin mixture is cool, then whisk in remaining nectar.
Transfer to a metal bowl and set bowl into a larger bowl half-filled with ice and cold water.
Let stand, stirring occasionally, until gelée is consistency of raw egg white, 15 to 25 minutes.
Put egg carton in a shallow baking pan and arrange glasses in carton, then tilt glasses to a 45-degree angle. Divide gelée among glasses. Carefully transfer pan with glasses to refrigerator and chill until gelée is set, at least 1 hour.
Pulse basil, sugar, and a pinch of salt in a food processor until finely chopped, then transfer to a bowl and add cream, stirring just until sugar is dissolved.
Sprinkle gelatin over water in a small saucepan and let stand 1 minute to soften. Cook over low heat, stirring, until gelatin is dissolved, 1 to 2 minutes.
Remove from heat and whisk in 1 tablespoon basil cream at a time until gelatin mixture is cool, then whisk in remaining cream.
Pour through a fine-mesh sieve into a metal bowl, pressing hard on solids and then discarding them.
Set bowl in a larger bowl half-filled with ice and cold water and let stand, stirring occasionally, until cream is consistency of raw egg white, 15 to 25 minutes.
Holding 1 glass of gelée at a 45-degree angle, slowly fill glass with basil cream, gradually righting glass as filled. Fill remaining glasses in same manner. Chill, covered, until set, at least 1 hour.
