This cookie is ready to party. Chewy in the middle, crisp on the edges, it is a giant cookie—10 inches across—that makes a perfect birthday or anytime celebration “cake” for cookie lovers. Another idea is to use it for sending good wishes in the role of an edible card, with a frosting greeting. Ice cream makes the perfect accompaniment to the wedge-shaped cookie slices. Vanilla, caramel, rum raisin, or butterscotch make particularly good choices.
makes 12 large cookie wedges • cookie making 20 minutes • cookie baking 350 degrees, for about 19 minutes
cookie
½ cup plus 2 tablespoons unbleached all-purpose flour
¼ teaspoon baking powder
¼ teaspoon baking soda
¼ teaspoon salt
½ teaspoon ground cinnamon
6 tablespoons (¾ stick) unsalted butter, at room temperature
½ cup packed dark brown sugar
¼ cup granulated sugar
1 large egg
1 teaspoon vanilla extract
1 cup oatmeal (not quick-cooking)
¾ cup raisins
½ cup walnuts, coarsely chopped
frosting
¾ cup powdered sugar
½ teaspoon vanilla extract
3 to 4 teaspoons water
Position a rack in the middle of the oven. Preheat the oven to 350 degrees. Trace a 9-inch circle on a piece of parchment paper and line a baking sheet with the paper, marked side down.
MAKE THE COOKIE. Sift the flour, baking powder, baking soda, salt, and cinnamon into a small bowl and set aside. In a large bowl, using an electric mixer on medium speed, beat the butter, brown sugar, and granulated sugar until smoothly blended, about 1 minute. Stop the mixer and scrape the sides of the bowl as needed during mixing. Add the egg and vanilla and mix until blended, about 30 seconds. On low speed, mix in the flour mixture to incorporate it. Mix in the oatmeal, then mix in the raisins and walnuts.
Drop spoonfuls of dough into the marked circle, then use a thin metal spatula to spread the dough evenly over the circle. Smooth the edges of the circle with the spatula.
Bake the cookie until the edges are light brown and the center is light golden, about 19 minutes. It will spread out about 1 inch. Let the cookie cool completely on the baking sheet on a wire rack.
MAKE THE FROSTING. In a small bowl, stir the powdered sugar and vanilla together with enough water to form a thick frosting. The frosting should hold its shape if you drizzle a little on a piece of paper. Spoon the frosting into a small self-sealing plastic freezer bag. Press out the excess air and seal the bag. Cut a small hole in one corner of the bag, about 1/16 inch long.
Hold the bag about 1 inch above the cookie at a slight angle and write your message by twisting the bag and gently squeezing to release a thin stream of frosting, moving the bag slowly to form thin letters or a design. Let the frosting firm at room temperature.
Once the frosting is set, the cookie can be covered and stored at room temperature for up to 2 days. Use a large sharp knife to cut the cookie into wedges to serve.