Preparation Steps:

• Step 1: Prepare the Baking Pan - Preheat your oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment paper, leaving some overhang on the sides.
• Step 2: Make the Cookie Base - In a mixing bowl, cream together the unsalted butter and confectioners sugar until light and fluffy. Add in the vanilla extract, followed by the all-purpose flour and cornstarch. Mix until just combined.
• Step 3: Bake the Cookie Layer - Spread the cookie dough evenly in the prepared pan. Bake for about 15-18 minutes, or until the edges are golden. Allow it to cool completely.
• Step 4: Prepare the Peanut Butter Filling - In another bowl, mix together the creamy peanut butter, melted unsalted butter, confectioners sugar, vanilla extract, and salt (if using) until smooth.
• Step 5: Assemble the Bars - Once the cookie base has cooled, spread the peanut butter mixture evenly over the top.
• Step 6: Melt the Chocolate - In a microwave-safe bowl, combine the semi-sweet chocolate chips and vegetable shortening (if using). Heat in the microwave in 30-second intervals, stirring until melted and smooth.
• Step 7: Top with Chocolate - Pour the melted chocolate over the peanut butter layer, spreading it evenly. Allow it to cool at room temperature or refrigerate to set.
• Step 8: Slice and Serve - Once set, lift the bars out using the parchment paper overhang. Slice into squares or rectangles and enjoy!