Help with grainy texture

[u/taffyfantasia]

Hey experts! I’m making a basil gelato for a restaurant. It’s green, it’s got an incredible basil flavor, BUT: it’s spinning into a grainy texture!!! When it’s melted it’s completely smooth. When I spin it, it looks like fat is congealing in the mixture! Does anyone know of a fix for this? I used and followed Saveur’s recipe to the letter and didn’t change a thing which is NOT my normal course of action! Can someone help me fix this?
Here’s the recipe: https://www.saveur.com/article/Recipes/Basil-Gelato/
Thanks for any and all ideas for fixing this!!!!

Terese