In a medium saucepan, combine ½ cup of sugar and ¼ cup of water over medium heat. Stir to dissolve, then boil for about 4-5 minutes until deep amber.

Remove from heat and mix in ¾ cup of unsalted butter and ¼ teaspoon of salt until smooth.

In a separate bowl, whisk together 3 egg yolks. Gradually drizzle in warm caramel while whisking constantly to temper the yolks.

Pour the egg yolk mixture back into the saucepan and cook over medium heat, whisking for about 3-4 minutes until thickened.

Stir in ½ teaspoon of vanilla extract and let cool to room temperature before refrigerating for at least 1 hour.

Whip 1 cup of heavy cream in a mixing bowl until stiff peaks form, taking about 3-5 minutes.

Gently fold the whipped cream into the cooled caramel mixture in batches until no streaks remain.

Spoon the mousse into serving dishes and refrigerate for at least 2 hours until set.

Serve chilled, garnished with whipped cream, a sprinkle of sea salt, or fresh berries if desired.