Stir together sweet potatoes, ¾ cup brown sugar, cinnamon and nutmeg until well combined. Spoon into a 10 to 11-inch deep quiche dish coated with cooking spray to form a bottom layer. Beat together egg yolks and sugar in a large glass bowl; stir in whipping cream and vanilla until thoroughly mixed. Cover and heat in microwave on HIGH for 3 minutes; stir and continue heating for another 3 minutes. Stir and heat another 2-3 minutes or until mixture is hot. Gently pour over pumpkin layer. Place dish in a shallow baking pan. Add hot water to baking pan to depth of 1-inch. Bake crème brulee at 325ºF for one hour or until the knife inserted near center comes out clean and the center shakes slightly. Remove from water bath and cool on wire rack. Refrigerate several hours or overnight. When ready to serve, sprinkle top of crème brulee evenly with additional ½ cup brown sugar. Place on baking pan and broil 5-8 inches from the heat until the sugar melts, or about 2 minutes. Let stand a couple of minutes for the sugar to harden. If desired, sprinkle toasted pecans around the rim of the crème brulee, add a dollop of whipped cream, and serve.

* Refrigerate leftover egg whites in a covered container for up to four days, or freeze for up to a year in a tightly sealed freezer container.