4. Add heated milk/cream to egg mixture. Add the heated milk/cream to the egg mixture gradually, so as not to scramble the eggs. Return the mixture to the saucepan, and cook over medium-low heat, stirring constantly, (with a wooden spoon is best) until the mixture thickens and coats the back of a spoon and holds a trail when you drag your finger through it, about 8 to 10 minutes.