Preheat oven to 350 degrees F (177 degrees C) and place oven rack in the center of the oven. Butter (or use a non stick cooking spray) an 8 x 8 inch (20 x 20 cm) pan.

Shortbread Base: In the bowl of your electric mixer, or with a hand mixer, beat the butter and sugar until light and fluffy. Add the flour and salt and beat until the dough just comes together. Press evenly onto the bottom of your greased pan and bake for about 20 to 25 minutes, or until pale golden in color. Remove from oven and place on a wire rack to cool while you make the filling.

Filling: In your food processor or with a hand mixer, beat the butter and sugar until light and fluffy. Beat in the eggs, one at a time, until incorporated. Scrape down the sides of the bowl as needed. Then beat in the corn syrup and vanilla extract. Stir in the flour, salt, and baking powder.

Sprinkle the raisins or nuts evenly over the baked shortbread base. Then pour the filling over the raisins (and/or nuts) and bake for about 20 - 25 minutes or until the filling is set. Remove from oven and place on a wire rack to cool. Serve at room temperature or chilled.

Makes 16 - 2 inch squares.