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.
In a medium bowl, whisk together the all-purpose flour, salt, and baking soda. Set this mixture aside.
In a large bowl, combine the melted butter, light brown sugar, and granulated sugar. Mix until well combined. Then, add the egg, egg yolk, and vanilla extract. Whisk until the mixture is smooth and creamy.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix. Fold in the chocolate chips gently.
Spread half of the cookie dough evenly into the prepared baking pan. Bake in the preheated oven for about 15-18 minutes, or until the edges are golden brown and the center is set but still soft. Remove from the oven and let it cool completely.
Once the cookie base is cooled, spread the softened chocolate chip cookie dough ice cream evenly over the cookie layer. Sprinkle the remaining chocolate chips on top.
Take the remaining cookie dough and drop spoonfuls over the ice cream layer. It's okay if some of the ice cream is exposed; it will still turn out delicious.
Return the pan to the oven and bake for an additional 15-18 minutes, or until the top is golden brown and set.
Allow the bars to cool completely in the pan. Once cooled, lift the bars out using the parchment paper overhang. Cut into squares, sprinkle with sea salt, and drizzle with hot fudge sauce if desired.
