Step 1

For the chicken: Combine the chicken, starch, wine, egg white and salt in a small bowl. Mix until evenly coated.

Step 2

For the sauce: Mix the stock, starch and both soy sauces in a small bowl.

Step 3

For the stir-fry: If using walnuts, bring a small saucepan of water to a boil. Add the walnuts, boil for 1 minute, then drain well. (A scrupulous Chinese chef would then peel them but I reckon life is too short to peel walnuts.)

Step 4

Lay the scallion whites on a board and smack briskly with the flat of a cleaver blade or a rolling pin to loosen them; then slice in half lengthwise and cut into ¾-inch pieces.

Step 5

Heat 1½ cups oil in a large wok or saucepan over high heat until a deep-fry thermometer registers 265 degrees. If you add a piece of chicken, the oil should sizzle gently but not violently around it. Add the marinated chicken and fry, separating the pieces, until they have turned pale and are separated but not cooked through, 3 to 5 minutes. Use a slotted spoon to transfer to a plate. Carefully pour out the oil and brush out the wok if browned bits remain.

Step 6

Return the wok to the stove over very high heat. When the wok is smoking hot, add the remaining 3 tablespoons oil and then the scallion whites. Stir-fry briefly until they are aromatic but not colored, about 30 seconds. Add the yellow bean paste and stir as it sizzles, about 1 minute. Return the chicken to the wok and stir. Splash the wine around the edges of the wok. Give the sauce a good stir and then pour into the center of the wok. Stir as the sauce thickens and cloaks the chicken, about 5 minutes. If using walnuts, quickly stir them in now. Serve immediately.