Place the oranges in a medium ovenproof dish, or divide among 4 ovenproof custard dishes. Spoon the Tangy Sabayon Sauce over the top (a couple tablespoons over each if using the individual dishes). Sprinkle with brown sugar. Place on a baking sheet, place under the broiler, and cook until golden to dark brown. Watch very closely for burning! Serve immediately.
Tangy Sabayon Sauce:
Place the egg yolks, sugar, and wine in a metal bowl. Place the bowl over a saucepan of barely simmering water, making a double boiler. Whisk the mixture constantly until it foams and then becomes creamy and doubles in size, about 5 minutes. Mixture should be uncomfortably warm to the touch, but not burning. Remove the pan from the heat and whisk in the sour cream.