Best Butter Tart Bars

Ingredients

• 1 ½ cups all-purpose flour
• 5 tbsp icing sugar
• ¾ cup cold unsalted butter
• ½ cup walnut pieces, lightly toasted
• ½ cup chocolate chips
• 1 cup packed light brown sugar
• ⅔ cup maple syrup or corn syrup
• 6 tbsp unsalted butter, melted
• 3 large eggs, at room temperature
• 1 tbsp white vinegar
• 2 tsp vanilla extract