Makes 25 Squares
Lining the pan with foil makes removal of the squares for cutting very easy (just lift out the entire block and place it on a cutting board to cut). For a nice presentation, trim 1/4 inch off the outer rim of the uncut baked block. The outside edges of all cut squares will then be neat.
11/2 cups (7.5 ounces) unbleached all-purpose flour
11/4 cups quick-cooking oats
1/3 cup (2.3 ounces) granulated sugar
1/3 cup packed light brown sugar
1/4 teaspoon baking soda
1/4 teaspoon salt
1/2 cup finely chopped pecans or almonds, or a combination
12 tablespoons (11/2 sticks) unsalted butter, cut into 12 pieces and softened but still cool
1 cup raspberry preserves
1. Adjust oven rack to lower-middle position and heat oven to 350 degrees. Spray 9-inch-square baking pan with nonstick cooking spray. Fold two 16-inch pieces of foil lengthwise to measure 8 inches wide. Fit one sheet in bottom of greased pan, pushing it into corners and up sides of pan (overhang will help in removal of baked squares). Fit second sheet in pan in same manner, perpendicular to first sheet. Spray foil with nonstick cooking spray.
2. In bowl of standing mixer, mix flour, oats, sugars, baking soda, salt, and nuts at low speed until combined, about 30 seconds. With mixer running at low speed, add butter pieces; continue to beat until mixture is well-blended and resembles wet sand, about 2 minutes.
3. Transfer 2/3 of mixture to prepared pan and use hands to press crumbs evenly into bottom. Bake until starting to brown, about 20 minutes. Using rubber spatula, spread preserves evenly over hot bottom crust; sprinkle remaining oat/nut mixture evenly over preserves. Bake until preserves bubble around edges and top is golden brown, about 30 minutes, rotating pan from front to back halfway through baking time. Cool on wire rack to room temperature, about 11/2 hours, then remove from pan using foil handles. Cut into 11/4- to 11/2-inch squares and serve.