In a bowl, whisk together all the marinade ingredients. Add in the beef and coat well. Leave to marinate for 10-15 minutes in the fridge.
Heat a wok on high fire. Add peanut oil, and swirl to coat.
Toss in the crushed Sichuan peppercorns and do a few quick stirs until fragrant.
Add in the beef, but keep the leftover marinade to the side. Pour in Shaoxing wine if using. Let sear for 1-2 minutes until slightly charred, then do a few quick stirs.
Add in bell pepper and the white parts of the scallions, and give it a few more stirs.
Keep the heat on high, add in the leftover marinade, and toss to coat all the ingredients. When the sauce starts to simmer, stir in the scallion greens and toasted sesame oil. Dish out and serve immediately with rice.