Steep the Sorrel: Bring 1½ cups of water to a high boil. Add the dried sorrel and boil for 2 minutes. Remove from heat and let steep for 30 minutes.
Strain: Strain the mixture and ensure you have 1 cup of sorrel liquid.
Combine Base Ingredients: In a saucepan over medium heat, combine the ketchup, molasses, soy sauce, garlic powder, onion powder, pepper sauce, and sorrel liquid.
Simmer: Stir and let the mixture simmer over medium-low heat for 10 minutes, stirring occasionally.
Thicken the Sauce: In a small bowl, mix the cornstarch and water until smooth with no lumps. Stir this slurry into the pot and continue simmering for 8–10 more minutes, or until the sauce thickens.
Adjust Consistency: If the sauce still runs off the spatula too easily, make another slurry with equal parts cornstarch and water and add gradually until the desired thickness is achieved.
Cool and Store: Once thick and smooth, remove from heat and pour into a clean glass or plastic bottle. If using plastic, allow the sauce to cool to room temperature first. Store in the refrigerator.
