Preheat the oven to 325 degrees F.
In a large bowl or in a food mixer, cream the butter until soft. Add the sugar, and beat until the mixture is light and fluffy.
Sift in the flour, and spices, if using, or grated zest, if using, and bring the mixture together to form the dough.
Using your hands, roll the dough into walnut-size balls, and place them slightly apart on an ungreased baking tray. Flatten the balls slightly with the back of a damp fork, and bake in the oven until they are light golden brown and slightly firm on top, about 13 to 15 minutes.
Carefully transfer the cookies to a wire rack to cool.
Variations: Poppy seed: Add 2 tablespoons of poppy seeds to the flour. Lemon: Add the finely grated zest of 1 lemon to the flour. Orange: Add the finely grated zest of 1 orange to the flour. White chocolate and orange: Dip the tops of the orange cookies in 50 grams (2 ounces) melted white chocolate, and then let set on parchment or waxed paper. Spices: cinnamon, mixed spice, ginger: Add 1 teaspoon of a ground spice to the flour. Crystallized ginger and dark chocolate: Add 2 tablespoons finely chopped crystallized ginger to the flour. When the cookies are baked and cooled, dip the tops in 2 ounces melted dark chocolate, and then let set on parchment or waxed paper. Double chocolate chip: Use 9 ounces all-purpose flour, and add 2 ounces sifted cocoa powder to the flour. Bring the dough together and mix in 4 1/2 ounces dark or white chocolate chips. White chocolate and dried cranberry: Add 1/4 cup chopped dried cranberries to the flour. When the cookies are baked and cooled, dip the tops in 2 ounces melted white chocolate and let set on parchment or waxed paper. Roll the leftover dough into a log shape, 3/4 to 1 1/4-inches in diameter, and then leave in the refrigerator for up to 2 weeks, or freeze for up to a couple of months. To bake: cut off slices, about 1/2-inch thick, and bake on a baking tray in a preheated oven. Always remove the cookies from their baking trays while they are still warm, otherwise they will stick.
Recipe courtesy of Rachel Allen