In a small bowl, use a fork to whisk the cornstarch and 3 Tbsp water into a slurry. Make sure to break up the clumps.
1/2 C Water, 1 Tbsp Corn Starch
In a small sauce pot, heat the vegetable oil over medium-low heat.
2 Tbsp Vegetable Oil
Once heated, add the ginger, garlic, and green onions. Cook 2-3 minutes until the garlic and onions turn translucent.
1/2 Tbsp Minced Ginger, 2 Cloves Garlic, 1 tsp Green Onion Whites
Add all the remaining ingredients, except the cornstarch slurry, to the pot (including the 1/2 C water). Bring to a boil.
1/4 C Ketchup, 1 Tbsp White Sugar, 1 Tbsp Soy Sauce, 2 tsp Rice Vinegar
Once boiling, cut the heat off and stir in the cornstarch slurry. The sauce should thicken almost instantly.
Use this sauce in stir fry dishes or serve it as a dip for egg rolls and spring rolls.