Prepare an 8x8-inch baking pan by lining with parchment paper with 2 inches of overhang. Set aside.
Add the white chocolate chips, 1 cup of milk chocolate chips, and the sweetened condensed milk to a microwave-safe bowl. Heat on high for 90 seconds, stirring every 30 seconds.
1½ cups white chocolate chips, 1½ cups milk chocolate chips, 14 ounces sweetened condensed milk
Stir until chips are melted. Mix in vanilla and salt.
1 teaspoon pure vanilla extract, ⅙ teaspoon kosher salt
Fold in cookie pieces and remaining ½ cup chocolate chips, then pour into the prepared pan and smooth out the surface.
1 cup chopped pre-made chocolate chip cookies
Top with cookie pieces and chocolate chips.
¼ cup chopped pre-made chocolate chip cookies, 2 tablespoons milk chocolate chips
Cover and cool in the refrigerator for 2-3 hours or until completely set. (For faster setting, freeze for 90 minutes)
Remove from pan using the parchment paper.
Cut into 24 square pieces.