Step 1

Add mirin and sugar to a small saucepan on medium heat and bring up to the boiling point. Add soy sauce and simmer 5 minutes. Allow to cool, and transfer to a glass jar.

Step 2

Add citrus juice, rice vinegar, water, and kombu, and put a lid on the jar. Store in the refrigerator for at least 4 hours. But you can store this for up to 2 weeks. Remove the kombu before using to make stir-fry.

Step 3

Mix the cornstarch with the ponzu sauce and keep it ready by the stove. Prepare all your vegetables for the stir-fry and keep them ready by the stove. Separate out the vegetables that take longer to cook (onions, carrots, bell peppers, and broccoli florets) from those that cook faster (green onions and button mushrooms).

Step 4

Heat a large skillet or wok on medium-high heat. Add garlic, ginger, red chili flakes, and sauté for 1-2 minutes. Add the vegetables that take the longest to cook first along with a pinch of salt. Use two wooden spoons to mix thoroughly and continuously. Sauté for about 3-4 minutes, until the vegetables start to soften.

Step 5

Add the remaining vegetables and sauté for about 3-4 minutes until the vegetables are cooked to your liking.

Step 6

Finally, give your sauce a stir and pour it in. Mix well, and cook for a minute or two more, until the sauce thickens.