The Ultimate Lemon Mousse

1.Pour the water in a small bowl, sprinkle the gelatin over it, and let stand until softened.

2.Put the bowl in a larger bowl of hot water and stir until the gelatin is dissolved and the liquid is clear.

3.Melt the butter in a heavy pan over medium-low heat.

4.Remove the pan from the heat and whisk in the sugar, egg yolks, and lemon juice.

5.Cook the mixture, stirring constantly, until it thickens and leaves a clear track when a path is drawn across the bottom of the pan with a spoon.

6.Do not let the mixture boil.

7.Remove the pan from the heat, stir in the gelatin mixture, and pour into a bowl.

8.Stir in the lemon zest and let cool to room temperature, whisking occasionally.

9.Beat the cream at high speed in a large bowl until it reaches stiff peaks.

10.Add the lemon mixture in batches, gently folding it in.

11.Divide the mousse between two stemmed glasses.

12.Refrigerate, loosely covered, for at least 2 hours or up to 2 days, until set.