This version serves as a base for Kumquat Creme Brulee.
Spread brown sugar evenly on baking sheet to air-dry, about 2 hours (time varies, depending on humidity). Push through sieve into small bowl, and set aside in dry, cool place. Heat oven to 250 degrees. Line an 11-by-17-inch baking pan with a Silpat (a French nonstick baking mat); make sure corners lie completely flat. Set aside.
Whisk together egg yolks and sugar in medium bowl until pale; set aside.
Place cream in medium saucepan. Split vanilla beans and scrape seeds into cream; add pods as well. Place pan over medium heat, and bring to a boil. Remove from heat, and slowly whisk into yolk mixture. Remove pods.
Position a baking pan the same size as the first on rack set in middle of oven; fill with boiling water one-third of way up sides of pan. Place Silpat-lined pan inside it, creating water bath. Pour cream mixture into baking pan, and bake for 45 minutes, or until just set. Carefully remove pans from oven, and separate them. Cool custard in pan on wire rack, then freeze until firm.
Using a 1-inch oval cutter, quickly cut ovals from frozen custard; transfer to parchment-lined baking sheet, and freeze until needed. If custard softens during cutting, return to freezer until firm.