1.   The sauce should not boil or the egg yolk will curdle.

2.   Add cornstarch solution and cook, stirring, until sauce boils and thickens.

3.   Cook over moderate heat, stirring constantly, until the sauce boils and thickens.

4.   Do not let the sauce boil.

5.   If necessary, let the sauce boil a bit to thicken.

6.   Stir cooking sauce, pour into skillet and stir until sauce boils and thickens.

7.   The sauce will boil vigorously.