De-seed the chillies by cutting and removing the seeds. If you prefer your Schezwan sauce hot, leave the seeds.
Soak the de-seeded chillies in hot water for 20-30 minutes. This softens the chillies, making them easier to grind into a smooth paste.
After soaking, drain the water and transfer the softened chillies to a blender. Add about ¼ cup of fresh water, diced tomatoes, and blend into a smooth paste. Keep the paste thick and not watery.
Heat oil in a heavy-bottomed pan. Add garlic, ginger, and coriander stalks once the oil is hot. Sauté this mixture until aromatic. No need to brown them. This step is crucial as it forms the aromatic base of the sauce.
Add the chili paste after the garlic and ginger are well sautéed. Be cautious, as the chili paste might splatter in the hot oil.
Stir well to combine everything, and let the mixture cook on medium heat for about 5 – 6 minutes. You’ll notice the oil separates from the paste, which is a sign that the chillies are cooked properly.
Season the sauce with soy sauce, vinegar, sugar, Sichuan peppers, and salt to taste.
Before turning off the heat, taste the sauce and adjust the seasoning if needed. You can add more salt, sugar, or vinegar-based on your taste preference.
Once the Schezwan sauce is cooked, let it cool completely before transferring it to an airtight container.