Combine the cream cheese, avocado, powdered sugar, vanilla extract, essential oil, and key lime juice into a bowl. Blend well with a mixer until the mixture is smooth and creamy. No lumps should remain.
If the filling is a too stiff you can add a teaspoon more key lime juice until it’s the right consistency.
Spoon the filling into the shells.
Chill in the refrigerator for at least 30 minutes. The filling will still be soft but will firm up just a little.
Garnish with blackberries, or other desired fruit.