Cut the meat into bite-sized pieces. Clean the carrots and leek and cut into fine strips. Clean the bean sprouts.
Fry the meat all around in 1 teaspoon of hot oil in a coated pan. Add the carrots and stock and cook covered for 3 minutes. Add the leek and bean sprouts and cook covered for another 5 minutes.
In the meantime, mix the peanut butter with 125 ml of water, cornstarch, soy sauce and lemon juice and then add to the pan. Bring to the boil again and season with salt and pepper.