1 cup (226 grams) unsalted butter, room temperature
1/3 cup (70 grams) light brown sugar
1 teaspoon pure vanilla extract
Preheat oven to 375 degrees F (190 degrees C) and place the wire oven rack in the center of the oven.Butter (or spray with a non stick cooking spray) a 9 x 9 inch (23 x 23 cm) pan.
Cranberry Filling: In a medium sized saucepan, place all the ingredients. Then, over medium-high heat, cook the ingredients until boiling. Continue to boil the filling until it becomes thick and syrupy, about 5 minutes. Remove from heat and let cool while you make the shortbread.
Shortbreads: In a separate bowl whisk the flour, cornstarch, and salt.
In the bowl of your electric mixer (or with a hand mixer), cream the butter until smooth (about 1 minute). Add the sugar and beat until smooth (about 2 minutes). Beat in the vanilla extract. Gently stir in the flour mixture just until incorporated.
Evenly press two-thirds of the shortbread into the bottom of the prepared pan. Then evenly spread the cranberry filling over the shortbread base, leaving a 1/4 inch border. With the remaining shortbread dough, using your fingers, crumble it over the top of the cranberry filling. Then lightly press the dough into the filling.
Bake in the preheated oven for about 30 minutes, or until golden brown on top. Remove from oven, place on a wire rack, and while still hot, cut into 16 squares. Allow to cool completely in pan.