Slice and Velvet the Beef: Place your steak in the freezer for 15-20 minutes to make it easier to slice. Using a sharp knife, slice the beef thinly (about ⅛-inch thick) against the grain. In a medium bowl, combine the sliced beef with the marinade ingredients: 2 tbsp soy sauce, 1 tbsp Shaoxing wine, 1 tbsp cornstarch, ½ tsp baking soda, and 1 tbsp vegetable oil. Mix well with your hands to ensure every piece is coated. Set aside to marinate for at least 30 minutes at room temperature.

Prepare the Aromatics: While the beef marinates, toast the Szechuan peppercorns in a small, dry skillet over medium-low heat for 2-3 minutes, shaking the pan frequently, until they are very fragrant. Be careful not to burn them. Let them cool, then grind them into a coarse powder using a spice grinder or mortar and pestle.

Mix the Sauce: In a small bowl, whisk together all the stir-fry sauce ingredients: chicken broth, 2 tbsp soy sauce, black vinegar, 1 tbsp Shaoxing wine, Doubanjiang, sugar, and 1 tsp cornstarch. Set aside.

Prepare Your Wok/Skillet: Place a wok or a large, heavy-bottomed skillet over high heat. Let it get screaming hot—you should see faint wisps of smoke.

First-Cook the Beef: Add 2 tablespoons of oil to the hot wok. Carefully add the marinated beef in a single layer (cook in two batches if necessary to avoid overcrowding). Sear for 1-2 minutes per side, until browned but not fully cooked through. The beef should be about 80% cooked. Remove the beef with a slotted spoon and set it aside on a plate.

Bloom the Spices: Reduce the heat to medium-high. Add the remaining 1-2 tablespoons of oil to the wok. Add the ground Szechuan peppercorns and the whole dried red chilies. Stir-fry for 30-45 seconds until they are fragrant and the chilies start to darken slightly. This step infuses the oil with their flavor.

Sauté the Aromatics: Add the garlic, ginger, and the white parts of the scallions to the wok. Stir-fry for another 30 seconds until fragrant.

Cook the Vegetables: Add the chopped onion and bell peppers to the wok. Turn the heat back up to high and stir-fry for 2-3 minutes. You want the vegetables to be crisp-tender, not soft and mushy.

Combine and Finish: Return the partially cooked beef to the wok. Give your sauce mixture a quick re-whisk (the cornstarch will have settled) and pour it all over the ingredients in the wok. Stir-fry continuously, tossing everything to coat. The sauce will bubble and thicken very quickly, usually within 1-2 minutes.

Serve Immediately: Turn off the heat. Stir in the toasted sesame oil. Transfer the stir-fry to a large serving platter. Garnish generously with the sliced green parts of the scallions and roasted peanuts or cashews, if using.