This recipe is courtesy of Gale Grand from "Baking with Julia" (William Morrow) by Dorie Greenspan and Julie Child.
FOR THE JAM
- 1 pound rhubarb, trimmed and cut into 1-inch pieces
- 1/2 cup granulated sugar
- 1/2 cup water
- 1 vanilla bean
FOR THE SHORTBREAD
- 4 cups all-purpose flour
- 2 teaspoons baking powder
- 1/4 teaspoon salt
- 1 pound (4 sticks) unsalted butter, room temperature
- 4 large egg yolks
- 2 cups granulated sugar
- Confectioners' sugar, for dusting
Make the jam: Combine rhubarb, sugar, and 1/2 cup water in a medium saucepan. Split vanilla bean, scrape the seeds into the pan, and toss in the pod. Bring to a simmer over low heat, cook, stirring often, until rhubarb softens and forms a soft mass, about 10 minutes. Remove and discard vanilla bean. Transfer to a shallow bowl and let cool. Can be made ahead and refrigerated in an airtight container, for up to one week. If refrigerated, return to room temperature before using. You may substitute 1 cup of your favorite jam or preserves for the homemade.
Make the shortbread: In a medium bowl, whisk together flour, baking powder, and salt. In the bowl of an electric mixer fitted with the paddle attachment, beat butter on high speed until pale and fluffy. Add egg yolks and sugar, and beat until sugar is dissolved and the mixture is light. Reduce mixer speed to low, and add the dry ingredients, mixing only until the ingredients are incorporated.
Turn the dough out onto a work surface and cut into two pieces. Shape each piece into a ball and wrap in plastic wrap. Place in freezer until firm, about 30 minutes. Can be made ahead and frozen for up to one month. Thaw in refrigerator overnight.
Assemble and bake: Preheat oven to 350 degrees with rack in center. Remove one ball of dough from freezer and, using the large holes on a box grater, grate the dough into a 9-by-13-inch baking dish. Pat the dough gently just to get it into the corners (you don't want to press it down), and spread with the rhubarb jam. Grate the remaining dough over the jam, and press it lightly to distribute it evenly. Bake until golden brown, about 40 minutes. Dust with confectioners' sugar as soon as it is removed from oven. Cool on a wire rack.
Cut the shortbread into bars when it is cool. You can cut whatever size bars please you, although as a rough guide, 3-inch squares, or rectangles 1 1/2 inches by 3 inches make nice servings. Store covered at room temperature for up to 2 days.