Butter Tart Squares

1/2 cup unsalted butter softened
1 cup brown sugar light or dark
2 tablespoons all-purpose flour*
4 large eggs
2 teaspoon vanilla extract
3/4 cup dark corn syrup*
2 tablespoons white vinegar*
1 cup raisins, currants or chopped walnuts – optional I use 1/2 cup currants and 1/2 cup chopped walnuts

Preheat the oven to 350F degrees. Line the pan with parchment paper, leaving an overhang around the edges.
In a large bowl beat the butter and powdered sugar until fluffy.
Mix in the flour – the mixture will be thick.
Press the mixture into the bottom of the pan.
Bake in the preheated oven for 15-20 minutes or until the top looks set and is a pale, golden color. Remove from the oven and leave the oven turned on.

Make the filling as the base layer is baking.
Beat the butter, brown sugar and flour until evenly combined.
Beat in the eggs and vanilla extract.
Mix in the corn syrup and vinegar. Stir in the optional raisins, currants or walnuts.
Pour the mixture over the gently baked crust.
Bake in the preheated oven for 30-35 minutes, or until the top looks set and if you give the pan a nudge the filling layer doesn’t look liquidy.
Remove from the oven and cool completely before slicing for clean cuts and to ensure that the bars are set.
When ready to slice, lift the bars out of the pan using the overhang of the parchment paper. Place on the cutting board and slice using a sharp knife. If the edges seem too crispy, simply slice off the edges.

For gooier bars, leave out the 2 tablespoons of flour from the filling.
Corn syrup can be substituted with pure maple syrup. However, I do recommend using corn syrup because it is how the recipe was developed.
The vinegar helps to cut the sweetness of the recipe – therefore I do not recommend leaving it out.
Feel free to use currants, raisins or chopped walnuts, or leave them out. I typically use 1/2 cup currants and 1/2 cup chopped walnuts.
I really recommend waiting for the bars to cool fully before slicing so that they are less messy.
Store bars in an airtight container in the fridge for up to 5 days after slicing. Bars can be frozen for up to 2 months, then thaw overnight in the fridge.
Nutrition information is an estimate only. It is based on 1 bar, assuming the recipe is made with 1 cup of raisins and sliced into 15 equal-sized squares.