Preheat your oven to 325°F (163°C). Prepare a baking dish with a water bath for even cooking.
In a saucepan, heat the heavy cream over medium heat until it begins to simmer. If using a vanilla bean, scrape the seeds into the cream and add the pod. Remove from heat and let steep.
In a separate bowl, whisk together the egg yolks and sugar until pale and creamy.
Slowly pour the warm cream into the egg mixture while whisking constantly to prevent scrambling.
Strain the mixture through a fine sieve to remove any lumps.
Divide the mixture evenly among the ramekins.
Place the ramekins in the prepared water bath and bake for 30-35 minutes, or until the custard is set but slightly wobbly in the center.
Remove from the oven, let cool, and refrigerate for at least 4 hours (or overnight).
Before serving, sprinkle sugar evenly over each custard and caramelize using a kitchen torch until golden brown and crisp.
Notes
For added flavor, try infusing the cream with citrus zest, espresso, or matcha powder.