Line a 9x9 inch baking pan with parchment paper and set aside. Place the mini chocolate chips in the freezer.
Using a hand or stand mixer, beat the butter, granulated sugar, and brown sugar until light and fluffy.
Place the flour in a microwave-safe bowl and heat in 20-second increments, stirring well between each heating until it has been heated for at least 1 minute and reaches 165°F. Be sure not to heat the flour without stirring and be sure to heat it in short increments and stir well so it doesn't clump.
Whisk the salt into the flour and then gradually beat the flour mixture into the butter mixture.
Heat the sweetened condensed milk and white chocolate chips in a medium saucepan over medium-low heat until melted and fully liquid, about 5-7 minutes. Do not overheat.
Remove the milk mixture from the heat and stir it into the prepared cookie dough until well combined. Once well combined, stir for another 3-5 minutes until the fudge is room temperature but no longer hot.
Fold in 1 cup of mini chocolate chips to combine. Do not overmix, or the chocolate will melt.
Pour the fudge into the prepared baking pan and spread it into an even layer.
Sprinkle the remaining mini chocolate chips over the top and press them gently into the fudge.
Cover the pan with plastic wrap and refrigerate for 2-3 hours or until firm.
Cut into squares and serve.
Notes
You can store Cookie Dough Fudge at room temperature for 1-2 days or in the refrigerator for about 1-2 weeks. Keep in mind that it may become slightly gooey or melty at room temperature, especially in warmer environments. For longer storage, freeze it for 2-3 months and thaw it in the refrigerator or at room temperature before serving.
Heating the flour is an optional step known as heat treating or pasteurizing. It reduces the risk of potential bacteria, such as E. coli or Salmonella, that may be present in raw flour. It's a safety measure to ensure the fudge is safe to consume.
You can heat treat the flour in the oven by spreading it on a baking sheet and baking it at 300°F (150°C) for 10 minutes, stirring halfway. Alternatively, you can heat treat it on the stovetop by placing it in a dry skillet or pan over medium heat, stirring constantly for about 5 minutes.