Mix the 1 cup of milk, and 1 cup of cream. Slowly add this to the sauce about a quarter cup at a time. Letting everything incorporate. When the milk is gone, the sauce should be a little thicker than you want it. Remove from heat. Add salt and spices, and the last quarter cup of milk. Mix well. This will bring the sauce down out of a simmer. Do this so the egg won't scramble. Stirring constantly, slowly add the egg. Just let it slowly drizzle, you have to stir fast or egg will clump.