Preheat oven to 325 degrees F.

In a medium bowl, whisk to combine yolks, sugar, and stevia.

In a medium saucepan, bring cream to a simmer. Whisk into yolk mixture. Whisk in pumpkin, vanilla, and spices.

Strain mixture through a fine-mesh sieve into a large measuring cup.

Divide mixture between six 6-ounce ramekins set in a roasting pan or other deep baking dish. Place pan in oven and pour in scalding hot water so it comes halfway up sides of dishes.

Bake until custards are set but jiggle slightly in the center, about 30 minutes. Transfer to a rack and let cool completely. Cover with plastic wrap and refrigerate until chilled, at least 2 hours and up to 24 hours.

Before serving, sprinkle custards with a layer of sugar and use a propane torch or broiler to caramelize sugar.