Preheat your oven to 325°F (165°C) and arrange four 6-ounce ramekins in a deep baking dish or roasting pan. This provides the foundation for your water bath, essential for gentle cooking.
Heat the cream and vanilla together in a medium saucepan over medium-low heat. If using a vanilla bean, add both the seeds and pod to the cream. Heat until small bubbles form around the edges (about 5 minutes)—don’t let it boil. Remove from heat and let steep for 10 minutes if using vanilla bean.
Whisk egg yolks, 1/4 cup sugar, and salt together in a medium bowl until the mixture lightens in color and becomes slightly thickened, about 2 minutes. The sugar should be mostly dissolved.
Gradually temper the eggs by slowly pouring about 1/4 cup of the warm cream into the egg mixture while whisking constantly. Continue adding the cream in a slow stream, whisking continuously to prevent the eggs from scrambling.
Strain the mixture through a fine-mesh sieve into a clean bowl or measuring cup with a pour spout. This removes any potential bits of cooked egg and ensures perfectly smooth custard.
Divide the custard evenly among the ramekins, filling them about 3/4 full. Place the baking dish on the oven rack, then carefully pour enough boiling water into the dish to reach halfway up the sides of the ramekins.
Bake for 35-40 minutes until the custards are set but still slightly jiggly in the center—they should wobble like gelatin when gently shaken. They will continue to set as they cool.
Cool the custards completely at room temperature, then cover each with plastic wrap and refrigerate for at least 2 hours or up to 3 days.
Just before serving, sprinkle 1-2 teaspoons of sugar evenly over each custard, rotating and tilting the ramekin to ensure complete coverage. Tap out any excess sugar.
Caramelize the sugar using a kitchen torch, moving it constantly over the surface until the sugar melts and turns a deep amber color. Let stand for 1-2 minutes until the sugar hardens into a crisp shell before serving.