Gather all the ingredients listed above. Having everything ready will make the process smooth and enjoyable.
In a mixing bowl, combine the soy sauce, molasses, sesame oil, and rice vinegar. Whisk these ingredients together until they are well blended.
Add the peanut butter, minced garlic, sriracha sauce, and ground pepper to the mixture. Continue to whisk until the peanut butter is fully incorporated, and the mixture is smooth.
In a small bowl, combine the water and cornstarch to create a slurry. Mix well to ensure there are no lumps. Then, add this mixture to your hoisin sauce. Stir well to distribute evenly.
Taste your homemade hoisin sauce and adjust the flavors as needed. You may want to add more molasses for sweetness, more sriracha for heat, or a little more soy sauce for saltiness.
Transfer your hoisin sauce to a storage container with a tight-fitting lid. It can be stored in the refrigerator for up to two weeks.