Creating these buttery caramel pudding cups is a straightforward process. Follow these numbered instructions for a successful dessert:

1. Prepare the Caramel Base: In a medium saucepan, combine the granulated sugar and water. Cook over medium heat, stirring occasionally, until the sugar dissolves completely. Increase the heat to high and cook without stirring until the mixture turns a deep amber color. This should take about 6-8 minutes.
2. Add Liquids: Carefully add the whole milk, heavy cream, and salt to the caramel. The mixture will bubble vigorously, so pour slowly. Stir until the caramel is fully dissolved into the milk and cream. Remove from heat.
3. Mix Egg Yolks and Cornstarch: In a separate bowl, whisk together the egg yolks and cornstarch until smooth.
4. Temper the Eggs: Slowly pour about a cup of the hot caramel mixture into the egg yolk mixture, whisking continuously to prevent the eggs from cooking.
5. Combine and Cook: Pour the tempered egg mixture back into the saucepan with the remaining caramel mixture. Return to medium heat and cook, whisking constantly, until the mixture thickens and begins to boil. This should take about 2-3 minutes.
6. Add Butter and Vanilla: Remove the saucepan from heat and stir in the vanilla extract and unsalted butter until fully incorporated.
7. Strain and Cool: Pour the pudding through a fine-mesh sieve into a large bowl to remove any lumps. Divide the pudding among serving cups or ramekins. Cover with plastic wrap, pressing directly onto the surface to prevent a skin from forming. Chill in the refrigerator for at least 2 hours or until set.
8. Serve: Before serving, top with a dollop of whipped cream and a drizzle of caramel sauce, if desired.