Trim and velvet the beef - Trim the beef into ½ inch strips. Coat the beef with ¼ t baking soda and a bit of water, and let rest for 15 minutes to denature the proteins. Rinse the beef (to remove the metallic taste of the baking soda - this is important!), and pat it dry. Then coat the beef strips with 1 T of tamari and 1 t cornstarch. Gently mix well until the cornstarch is no longer visible, then fold in 1 T wine and 1 t sesame oil. Set aside in the fridge for at least 10-15 minutes.
Prep the veg (Mise en Place) - Destem and core the peppers. Slice into 1½ to 2-inch planks. Peel and slice the onion into large pieces, about the same size as the peppers. Combine peppers and onions in a bowl and set aside. Peel and mince the garlic. Grate the ginger on a rasp. Trim and thinly slice the scallions. Combine garlic, ginger, and scallion in a bowl and set aside.
Make the stir-fry sauce - Combine 3 T soy sauce with 2 T cornstarch, and stir with a fork to form a slurry. Add ⅓ cup wine, ⅓ cup chicken stock, 1 T sesame oil, 1 T sugar, and ½ t pepper. Set aside.
Stir-fry in batches - When ready to cook, heat 1 T oil in a wok over high heat until smoking. Add half of the beef and cook without moving until well seared, about 1 minute. Continue cooking while stirring and tossing until lightly cooked but still pink in spots, about 1 minute. Transfer to a large bowl. Repeat with 1 more tablespoon of oil and remaining beef, adding beef to the same bowl. Wipe out wok. Repeat with 1 more T oil and half of peppers and onions. Transfer to the bowl with beef. Repeat with remaining oil and remaining peppers and onions.
Finish - Return wok to high heat until smoking. Return the beef, peppers, and onions to the wok and add the garlic, ginger, and scallions. Cook, tossing and stirring until fragrant, about 30 seconds. Add sauce and cook, tossing and stirring constantly until slightly thickened. Serve right away with rice.