Heat 8 wineglasses by pouring very hot water into them. Drain water; add 2 tablespoons whiskey to each glass.
Stir remaining 4 tablespoons sugar into coffee until dissolved. For each drink, fill glass with coffee to within 1 1/4 inch from top. Hold large spoon upside down over top of glass; gradually pour whipped cream over back of spoon onto coffee (cream should float on top, about 1 inch thick). Sprinkle with nutmeg and cinnamon, if desired.