Preheat your oven to 350°F (175°C). This ensures your bars bake evenly.
Line a 9x13 inch baking pan with parchment paper, leaving some overhang on the sides for easy removal later.
In a large mixing bowl, combine the softened butter, peanut butter, brown sugar, and granulated sugar. Using an electric mixer, beat the mixture on medium speed until it’s light and fluffy.
Crack in the egg and add the vanilla extract. Mix until fully incorporated.
In a separate bowl, whisk together the flour, salt, and baking soda. Gradually add the dry ingredients to the peanut butter mixture, mixing until just combined.
Gently fold in 2 cups of the chocolate chips, reserving 1 cup for later use.
Transfer the cookie dough into the prepared baking pan, spreading it evenly across the bottom.
Bake in the preheated oven for 15-20 minutes, or until the edges are golden and a toothpick inserted in the center comes out clean.
While the cookie layer is baking, combine the sweetened condensed milk and the remaining 1 cup of chocolate chips in a saucepan over low heat. Stir until melted and smooth.
Once the cookie layer is done, remove it from the oven and pour the fudge mixture over the top. Spread it evenly and return the pan to the oven for an additional 10-15 minutes, until the fudge is set.
Allow the bars to cool completely in the pan before lifting them out using the parchment paper overhang. Cut into squares and enjoy your Peanut Butter Cookie Fudge Bars!
