1. In a medium saucepan, combine the heavy cream, whole milk, and maple syrup. Heat over medium heat until just simmering, stirring occasionally. Do not bring to a full boil.
2. In a separate bowl, whisk together the egg yolks, sugar, vanilla extract, and salt until smooth and pale.
3. Gradually add the warm cream mixture to the egg yolk mixture in a slow stream, whisking constantly to prevent the eggs from curdling.
4. Pour the custard mixture back into the saucepan and cook over low heat, stirring constantly, until the custard thickens and coats the back of a spoon (about 8-10 minutes). Be sure to avoid boiling the custard.
5. Once thickened, strain the custard through a fine mesh sieve into a clean bowl to remove any curdled bits. Allow the custard to cool slightly before dividing it into individual serving dishes.

Prepare the Salted Hazelnut Caramel Sauce: 6. In a medium saucepan, melt the sugar over medium heat, stirring occasionally. Once the sugar melts and becomes golden, carefully add the butter and stir until fully incorporated.

7. Slowly pour in the heavy cream, whisking constantly. Be cautious, as the mixture may bubble up. Continue to stir until smooth.
8. Stir in the sea salt and toasted hazelnuts. Allow the sauce to simmer for an additional 2 minutes, then remove from heat and let it cool slightly.

Assemble the Dessert: 9. Once the custard has cooled to room temperature or is slightly chilled, spoon the salted hazelnut caramel sauce over the top of each serving of custard.

10. Serve immediately, or refrigerate for later. Enjoy!