Preheat your oven to 325 (F).

In a medium-sized heavy-bottomed sauce pot, use a wooden spoon to combine 2 tablespoons unsalted butter and 1/2 cup brown sugar and cook over medium heat. The sugar and butter will separate at first, but as the sugar melts it will become easier to blend them together. Cook until the mixture just starts to brown and smoke slightly.

Slowly add 2 cups heavy cream, a half cup at a time. The sugar and butter mixture will sputter and sieze up (turn back into solid sugar) as you add the cold cream — don't worry about this! Just continue cooking the mixture until the seized sugar dissolves again.

Once the seized sugar has dissolved, add 1 split vanilla bean pod and 1/8 teaspoon salt, using the wooden spoon to gently stir the vanilla beans and salt into the mixture. Remove from heat and set aside — this is your butterscotch mixture.

In a small, heatproof bowl, whisk together 4 egg yolks. Use a tablespoon measure to slowly add 1 tablespoon of butterscotch into the yolks as you whisk them. You are just adding enough of the butterscotch mixture to warm the yolks slightly. Continue repeating this step until the yolk mixture is warm to the touch — I added about 4 or 5 tablespoons of butterscotch to the yolks before I got them to the temperature I wanted.

Once the yolks are warm to the touch, pour the yolks back into the butterscotch mixture and gently whisk them together.

Strain the mixture into a medium bowl to remove the vanilla bean pod. Carefully divide the custard into four or five 4-ounce ramekins. I was super meticulous and carefully poured 4 ounces of custard into each ramekin, and found I had enough for a fifth ramekin.

Carefully place the filled ramekins into a baking pan, and fill the baking pan with boiling water. It is important that the water in the pan is hot and comes half way up the side of the ramekins so that it will reach oven temperature quickly — using cool water will prevent them from baking properly, so be sure to use boiling water. Cover the pan with aluminum foil, making sure to poke holes up top.

Bake for 25 - 40 minutes. Your baking time depends on the temperature of the mixture when you put it in the oven. Check the ramekins after 25 minutes and gauge how much longer they need by tapping the side of each ramekin. If it ripples like water, it needs to bake longer. If it moves like set jello, then it's finished. DO NOT OVERBAKE or they will be grainy and I will cry. My ramekins were finished between 30 - 35 minutes.

Just before serving, spread a thick, even layer of unsweetened crème fraiche over the top of each custard.