Preheat the oven to 325°F (160°C).

In a blender, combine heavy cream, mashed sweet potatoes, egg yolks, sugar, vanilla extract, and salt. Blend until smooth.

Pour the mixture into ramekins and place them in a baking dish. Fill the baking dish with hot water halfway up the sides of the ramekins.

Bake for 30 minutes or until set. Remove from the oven and let cool.

Sprinkle granulated sugar evenly over the cooled creme brulee.

Using a kitchen torch, caramelize the sugar until golden brown.

Let it sit for a few minutes before serving.