Preheat oven to 325°F and line a standard cupcake pan with cupcake liners.

In a bowl, combine graham cracker crumbs, melted butter, and granulated sugar. Mix until the crumbs are moist and well combined.

Portion 2 tablespoons of the graham cracker mixture into each cupcake liner and press down to create a flat, even base. Bake for 5-6 minutes and let cool. The crust should be lightly baked but not browned.

In a medium bowl, combine the softened cream cheese and sour cream. Mix on medium speed with a hand mixer until completely smooth.

Add the egg yolks, sugar, salt, and vanilla. Mix until smooth, avoiding high speed to prevent incorporating too much air.

Whip the egg whites to stiff peaks and gently fold them into the cheesecake mixture.

Transfer the cheesecake filling into a piping bag fitted with a large round tip or use a large freezer bag with the corner cut off.

Fill the cupcake liners with cheesecake filling until 3/4 full. You can fill them a bit closer to the top, just don’t fill to the very rim.

Boil 6-7 cups of water. Place the cupcake pan on a rimmed half sheet pan and put it in the oven. Pour the boiling water into the half sheet pan until it comes halfway up the sides of the cupcake wells.

Bake for 18-23 minutes, or until the centers are just barely jiggly. Remove the cupcake pan from the water bath and let cool for 1 hour at room temperature, then refrigerate for at least 2 hours until thoroughly chilled.

In a large, heavy-bottom saucepan, heat the sugar on medium-low to medium heat. Let the sugar begin to melt without stirring too often. Once it starts to melt, stir occasionally.

To prevent sugar crystals from forming, use a pastry brush dipped in water to wash down the sides of the pan.

Continue to stir the caramel as it melts. Once it reaches the color of a brown paper bag, add the butter. The darker the caramel, the richer the flavor.

Add the salt and warm heavy cream, whisking rapidly as the cream goes into the caramel.

Strain the caramel to remove any seized bits and place it in the fridge to cool.

Remove the cheesecakes and caramel from the fridge. If the caramel is stiff, warm it in the microwave for 20-30 seconds.

Top the cheesecakes with as much caramel as you desire. Sprinkle with extra fleur de sel and add whipped cream if you like. Enjoy!