In small bowl, stir icing sugar, 1 tablespoon of the eggnog and the vanilla. Add remaining eggnog, 1 teaspoon at a time, until easily drizzled. Drizzle glaze evenly over cooled bars. Sprinkle with remaining 2 tablespoons toffee bits and the nutmeg. Let glaze set before cutting into 9 rows by 4 rows.