Beat in the vanilla. Add the eggs one at a time, beating for 1 minute after each egg goes in. Reduce the mixer speed to low and add the dry ingredients in 3 portions, mixing only until each addition is incorporated. On low speed, or by hand with a rubber spatula, mix in the chocolate and nuts. ( The dough can be covered and refrigerated for up to 3 days or frozen. If you’d like, you can freeze rounded tablespoonfuls of dough, ready for baking. Freeze the mounds on a lined baking sheet, then bag them when they’re solid. There’s no need to defrost the dough before baking – just add another minute or two to the baking time.)