Chinese Sweet and Sour Sauce

In a small bowl, whisk together the ketchup, rice vinegar, brown sugar, and soy sauce until well combined. Set aside.
In another small bowl, dissolve the cornstarch in water to create a slurry. Set aside.
Heat vegetable oil in a small saucepan over medium heat. Add minced garlic, minced ginger, and crushed red pepper flakes (if using). Cook for 1-2 minutes until fragrant.
Pour in the ketchup mixture and bring to a simmer. Let it cook for 2-3 minutes, stirring occasionally.
Stir the cornstarch slurry once more to ensure it's well combined, then pour it into the saucepan. Stir continuously until the sauce thickens, about 1-2 minutes.
Remove the sauce from heat and let it cool slightly before serving.
Use the Chinese Sweet and Sour Sauce as a dip for your favorite appetizers or as a sauce for stir-fries. Enjoy!