Marbled Peanut Butter Shortbread

In food processor, finely grind together nuts, granulated sugar and salt just until starting to clump. Set aside.

In bowl and using wooden spoon, cream butter with brown sugar until light; stir in vanilla and peanut mixture. In separate bowl, whisk together all-purpose flour, rice flour and baking powder; stir into butter mixture just until combined. Remove one-third of the dough to small bowl; stir in chocolate just until combined.

Alternating colours to create marble pattern, press dough into parchment paper–lined 8- or 9-inch (2 or 2.5 L) square metal cake pan. Score into 25 squares. Using fork, prick once or twice per square.

Bake in 325°F (160°C) oven until lightly browned and tester comes out clean, 45 to 50 minutes. Let cool in pan on rack for 10 minutes. Using sharp knife and leaving in pan, cut through score lines. Let cool completely. (Make-ahead: Store layered between waxed paper in airtight container for up to 1 week or freeze for up to 1 month.)

Source : Canadian Living Magazine: December 2009