In a heavy saucepan, combine sugar and water over medium-low heat until the sugar dissolves. Increase the heat and bring to a low boil, swirling the saucepan gently, but not stirring. Keep the mixture constantly moving.
Simmer until the mixture is syrupy and a deep caramel color, about 5-10 minutes.
Remove mixture from heat and whisk in butter and cream, being mindful that the mixture will spit and sizzle, so be careful. Whisky vigorously until it reaches a smooth, sticky consistency.
Whisk in vanilla and fleur de sel.
Stir in whole pecans.
Depending on the recipe, allow your caramel sauce to cool or serve hot.
If you've tried this recipe, come back and let us know how it was!