Butter Tart Squares

Indulge in homemade Butter Tart Squares with a rich shortbread base and a luscious brown sugar filling. Perfect with or without nuts and raisins, these squares are a delightful twist on a classic dessert, baked to perfection in just one hour!
Base Layer:
1 cup of unsalted butter softened to room temperature
½ cup of confectioners’ sugar
2 ¼ cups of all-purpose flour sifted
Butter Tart Filling:
½ cup of unsalted butter softened to room temperature
1 cup of light or dark brown sugar firmly packed
2 tablespoons of all-purpose flour
4 large eggs preferably organic
2 teaspoons of pure vanilla extract
¾ cup of dark corn syrup
2 tablespoons of white vinegar
1 cup of optional ingredients such as raisins currants, or chopped walnuts (a combination of ½ cup currants and ½ cup chopped walnuts is recommended)
For the Base Layer:
Preheat the oven to a temperature of 350°F (175°C). Prepare a baking pan by lining it with parchment paper, allowing the paper to overhang on the sides to facilitate easy removal of the baked product.
In a capacious mixing bowl, cream together the softened unsalted butter and confectioners’ sugar until the mixture achieves a fluffy consistency.
Gradually incorporate the sifted all-purpose flour into the butter and sugar mixture until it becomes thick and homogenous.
Transfer the dough into the bottom of the prepared baking pan, pressing it down firmly to create an even base.
Commence baking in the preheated oven for a duration of 15 to 20 minutes, or until the surface appears to be set and has obtained a pale golden hue. Once achieved, remove from the oven while maintaining the oven’s set temperature.
For the Filling Layer:
While the base layer is in the oven, prepare the filling. Begin by beating the softened unsalted butter, brown sugar, and all-purpose flour together until fully combined and smooth.
Continue by adding the eggs and pure vanilla extract to the mixture, ensuring to beat well after each addition.
Proceed to incorporate the dark corn syrup and white vinegar into the mixture, stirring thoroughly. If opting to include raisins, currants, or chopped walnuts, fold these into the mixture at this juncture.
Once the base layer has been removed from the oven, pour the prepared filling over it, ensuring an even distribution.
Return the pan to the oven, allowing it to bake for an additional 30 to 35 minutes. The filling should appear set and should not exhibit a liquid consistency when the pan is gently nudged.
Upon completion of baking, set aside to cool to room temperature. This step is crucial to ensure the squares are properly set and facilitate clean slicing.
For serving, utilize the overhanging parchment paper to lift the baked squares from the pan. Transfer to a cutting board and, with a sharp knife, proceed to slice into the desired number of squares. If the edges of the squares seem overly crisp, they may be trimmed at the baker’s discretion.