In a wok, heat an inch of oil. Fry beef in small batches until crisp and browned on the edges; add to a bowl containing Szechuan sauce to marinate once cooked.
Remove wok from heat and discard oil. Return the wok to heat and add 1/4 C of water to deglaze. Using a metal spoon, scrape up the fond from the bottom of the wok.
Add vegetables to the wok and cook until carrots begin to soften, 5-7 minutes.
Add back to the wok the beef, the Szechuan sauce marinade, and the brown sauce. Bring to a boil, then reduce heat to simmer. Add salt to taste. If the sauce needs additional thickening, use a few teaspoons of a cornstarch and water slurry.