Preheat your oven to 350°F (175°C) to ensure even baking.
Grease a 9x13 inch baking dish with cooking spray or line it with parchment paper.
In a medium bowl, whisk together the flour, salt, baking soda, cinnamon, and allspice until well combined. Set aside.
In a large mixing bowl, beat the butter and sugar together until light and fluffy, about 2-3 minutes.
Mix in the molasses and egg until fully incorporated.
Gradually add the dry mixture to the wet ingredients, mixing until just combined.
Gently fold in the white chocolate chips or your choice of candy.
Pour the batter into the prepared baking dish, spreading it evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bars to cool in the pan for about 10 minutes before transferring to a wire rack to cool completely. Once cooled, cut into squares.
