Cornstarch (Best Option)
1 tablespoon cornstarch per 1 tablespoon arrowroot powderCornstarch is a starch extracted from corn, widely used as a thickening agent. It gelatinizes at a similar temperature to arrowroot and creates a smooth, creamy texture, making it an excellent substitute in Panna Cotta. It thickens by absorbing water and swelling, which helps set the dessert without altering its flavor.
When using cornstarch, mix it with cold liquid before adding to the warm cream mixture to prevent clumping. Cook the mixture until it thickens and becomes translucent to ensure full gelatinization. Avoid overcooking as it can break down and thin out.
Compared to arrowroot, cornstarch may produce a slightly less glossy finish and a marginally denser texture, but it remains very close to the original in mouthfeel and appearance.