1.   Add the oats to thicken the mixture and stir until it is nice and creamy.

2.   Add cream, sugar and lemon peel, and beat until mixture is partly thickened.

3.   Chill, stirring occasionally, until mixture is thickened but not completely set.

4.   Cook over high heat until mixture is thickened and water is evaporated.

5.   I always include chayote, a pale green squash that tastes like cooked pears and helps thicken the mixture, almost like a flour-based roux.

6.   In any case, finish the sauce with a sprinkling of Parmesan, which not only adds its distinctive sharpness, but also thickens the mixture even further.

7.   Place over medium heat, and stir until mixture is thickened, one to two minutes.

8.   When mixture is slightly thickened, add remaining butter and salt to taste.