Set the oven to 325°F (165°C). Arrange the ramekins in a large baking dish with high sides for the water bath. If you don’t have 1 pan large enough, bake them in a couple pans.
In a medium saucepan, combine heavy cream, milk, cinnamon, nutmeg, ginger, cloves, and a pinch of salt. Heat over medium, stirring occasionally, until it just starts to simmer. Remove from heat and let it steep for 15 minutes.
In a large bowl, whisk egg yolks and 1/2 cup (100g) sugar until light and creamy.
Slowly whisk the warm cream mixture into the yolk mixture a little at a time to temper (this keeps the eggs from scrambling).
Strain the custard through a fine sieve into a bowl to catch any lumps.
Stir in the pumpkin purée until smooth.
Place ramekins in a large baking pan. Divide custard between each ramekin, filling to the top. Carefully fill the pan with about a 1/2 inch of the warm water.
Bake until the edges are set and centers are a little jiggly. The time depends on the depth of your ramekins. My ramekins are 1-inch and the custard takes 35 minutes. Begin checking them at 30 minutes. For a more accurate sign, they’re done when an instant read thermometer registers 170°F (77°C). Remove pan from the oven and, using an oven mitt, remove the ramekins from the pan. Place on a wire rack to cool for at least 1 hour. Place in the refrigerator, loosely covered, and chill for at least 4 hours and up to 2 days before topping.
Just before serving, sprinkle 1 teaspoon of granulated sugar evenly over each custard. Use a kitchen torch to caramelize the sugar until golden brown. Let the caramelized top cool briefly before serving. (Caramelized topping is best enjoyed right away.)