Bring sugar, butter and eggnog to a full boil in a heavy medium-size saucepan. Continue to boiling over medium heat until candy thermometer reaches 234 degrees, stir constantly to prevent scorching. Remove from heat and stir in the white chocolate and nutmeg, stirring until the chocolate is melted. Add marshmallow creme and vanilla extract. Beat until well blended. Pour into a buttered 8 or 9-inch square pan. Cool, then cut into squares. Store in an airtight container in the refrigerator. May be frozen for up to three weeks.