Chocolate Chip Peanut-butter Bars

Preheat oven to 350°F. Place parchment paper in an 8x8 baking dish. In a bowl, using a stand mixer fitted-with paddle attachment, beat the butter for 2 minutes on medium speed till smooth. Add brown sugar while beating on medium speed until combined, about 2 minute. Mix in egg + yolk and vanilla on medium-high speed for about a minute. Scrape down the sides of the bowl. In a separate bowl, combine flour, cornstarch, baking soda and salt. On low speed, slowly mix into the wet ingredients until combined. We mix in 1/4 cup at a time, till fully combined. Add 1/2 cup of chocolate chips and mix for 10 seconds till combined. Add 1/2 cup of peanut butter chips and mix for 10 seconds. Take half the cookie dough and press the dough evenly into the prepared pan. In a small bowl microwave peanut-butter and heavy cream for 30 seconds (intervals of 15 seconds). Spread peanut-butter on top of cookie dough. Take other half of the cookie dough and press down evenly on top of the peanut-butter layer. Bake for 30 minutes or till the cookie bar is lightly golden brown. Remove from the oven, to cool completely, about an hour. Once cooled, use a sharp knife to cut! Enjoy!