My favorite type of starch to use for a crunchy exterior, whether it’s for tofu or fried chicken, is tapioca starch (also known as tapioca flour). Tapioca starch can be easily found in Asian markets. If you have a hard time find it though, another great alternative is cornstarch!
Another trick to getting a premium crisp to your tofu is by letting the tofu sit for about 5 minutes after they’re tossed in the tapioca starch. This allows the starch to absorb onto the tofu, as opposed to falling off while cooking.