Kung pao (gong bao) shrimp - chinese grandma

Ingredients

• 1 pound shrimp, peeled and deveined
• 2 tablespoons cornstarch
• Cooking oil
• 1/4 cup chopped onion
• 1 1/4 cups vegetables, cut thin/small enough to cook quickly (eg diced green/red bell pepper or zucchini, thinly diagonal-sliced carrot or celery)
• 1 clove garlic, chopped
• 1 slice ginger, minced (optional)
• 2 dried red chili peppers
• 1/4 cup roasted peanuts, plus more for serving alongside
• Cilantro, for garnish (optional)
• 2 tablespoons soy sauce (Kikkoman or dark)
• 2 tablespoons white vinegar
• 2 teaspoons sugar
• 1 teaspoon cornstarch