Add 3/4 cup of bourbon for every 2 quarts of store-bought eggnog. Dark rum or brandy are good substitutes for bourbon. This is a general guideline. Add more or less, depending upon what taste is preferred.
For a festive drink, combine the bourbon and chilled eggnog in a punchbowl. Whip one cup of heavy cream until it is thick but not stiff. Because the eggnog is very rich, sugar does not need to be added to the cream. However, if a sweeter drink is preferred, add two tablespoons of powdered sugar and one teaspoon of vanilla extract near the end of the whipping time. Fold the whipped cream into the punch. It does not need to be mixed thoroughly. Small mounds of whipped cream are an attractive touch. Sprinkle the surface of the punch with ground nutmeg.