The Ultimate Lemon Mousse

Directions

1. 1
   Pour the water into a small bowl, sprinkle the gelatin over the water and let stand about 10 minutes, or until softened.
2. 2
   Place the bowl in a larger bowl of hot water, and stir until the gelatin has dissolved and the liquid is clear.
3. 3
   Meanwhile, melt the butter in a large heavy saucepan over med-low heat.
4. 4
   Remove the pan from the heat and whisk in the sugar, zest, lemon juice, and salt.
5. 5
   Whisk in the yolks until smooth; cook mixture, stirring constantly, until it thickens and leaves a path on the back of a wooden spoon when a finger is drawn across it; do not allow the mixture to boil.
6. 6
   Remove the pan from the heat, stir in the gelatin mixture and immediately pour through a strainer into a bowl.
7. 7
   Let cool to room temperature, whisking occasionally.
8. 8
   Beat the cream with an electric mixer on high speed in a large bowl just until the cream forms stiff peaks.
9. 9
   Add the cream to the lemon mixture in 3 batches, gently folding it in with a whisk or a rubber spatula just until blended.
10. 10
    Divide the mousse evenly between 4 stemmed glasses; refrigerate, loosely covered, for at least 2 hours or up to 2 days, until set and thoroughly chilled.