Brown butter in a small saucepan. Caramelize pumpkin puree in the butter for a few minutes. Add salt and spices, and whisk for another minute.
Add heavy whipping cream and whisk until smooth. Continue to whisk over low heat until bubbles form along the edges of the pan.
In a small bowl, whisk egg yolks, vanilla extract, and brown sugar until smooth. In a steady stream, whisk ¼ cup of hot cream into egg yolk and sugar mixture to temper the eggs. Once combined, whisk egg mixture in a slow, steady stream into saucepan. Boil a kettle of water.
Place 5 ramekins inside a deep roasting pan. Transfer custard to a large measuring cup for easier pouring. Fill ramekins with pumpkin custard mixture, then place on the center rack in the oven.
Pour hot water into pan ½ way up the sides of the ramikins, then bake for 50-60 minutes or until edges are set and center is slightly jiggly. Cool on a wire rack, then chill in the fridge for 4 hours.
Just before serving, sprinkle 2 teaspoons of sugar over the top of each custard, then use a kitchen torch to caramelize the sugar until it turns amber. Serve within a few hours.