Instructions

• Preheat oven to 375°F (190°C). Position a rack in the middle of the oven. Line a 13x9x2-inch baking pan with parchment paper leaving about a 2-inch overhang on the long sides; lightly coat the parchment with cooking spray.
• Make the shortbread base: in a large bowl whisk together 2 cups all purpose flour, 1/3 cup granulated sugar, 1/4 teaspoon kosher salt, and 1/2 teaspoon baking powder.
• Add 3/4 cup chilled unsalted butter (cut into small pieces) to the flour mixture. Use a pastry blender, two knives, or a fork to cut the butter into the dry ingredients until the mixture looks sandy and forms fine crumbs.
• In a small measuring cup stir together 3 tablespoons milk and 1 teaspoon almond extract. Pour this liquid over the crumb mixture and stir just until moistened throughout; the dough will remain crumbly. Do not overwork.
• Transfer the crumbly dough to the prepared pan. Press it evenly and firmly into the bottom of the pan to form an even layer.
• Bake the crust for 12–15 minutes, until the center is just set and the edges are beginning to turn light brown. Remove the pan from the oven and leave the oven on.
• While the crust is baking, make the oat crumble topping: in a medium bowl whisk together 1 1/2 cups all purpose flour, 1/2 cup light brown sugar (lightly packed), 1/4 cup granulated sugar, 1/2 teaspoon kosher salt, 1/2 teaspoon baking powder, 1/2 teaspoon ground cinnamon, and 1/8 teaspoon ground cardamom (optional). Stir in 1/2 cup rolled oats.
• Add 3/4 cup chilled unsalted butter (cut into small pieces) to the topping mixture. Cut the butter into the dry ingredients with a pastry blender, two knives, or a fork until the mixture is crumbly and holds together in small clumps.
• Spread 1 1/2 cups jam or fruit preserves in an even layer over the hot crust. Use a spatula or the back of a spoon to smooth it, taking care not to press through the crust.
• Sprinkle the prepared crumble topping evenly over the jam layer so the jam is fully covered.
• Return the pan to the oven and bake 25–30 minutes, until the crumble topping is light golden brown.
• Remove the bars from the oven and let them cool completely in the pan on a wire rack (cooling completely will help them set and make slicing cleaner).
• Use the parchment overhang to lift the bars from the pan. If desired, dust with powdered sugar, then slice into bars and serve.