Line an 8X8-inch baking dish with a parchment paper or foil sling. Place mini chocolate chips in freezer. Heat the flour in a microwave-safe bowl in the microwave for 90 seconds to kill any bacteria. Set aside to cool.
1 cup mini chocolate chips, 1 ¼ cups (176g) all-purpose flour
In a medium bowl, beat butter, brown sugar, and granulated sugar until light and creamy, about 2 minutes.
½ cup salted butter, ½ cup light brown sugar, 3 Tablespoons granulated sugar
Add cream and vanilla, then mix again to combine.
2 Tablespoons heavy cream, 1 teaspoon vanilla extract
Add flour and salt, mixing just until no streaks of flour remain.
¼ teaspoon salt
Combine white chocolate chips and sweetened condensed milk in a small, microwave-safe bowl. Heat for 90 seconds, stirring every 30 seconds, until white chocolate is melted and smooth.
1 cup white chocolate chips, 1 (14-ounce) can sweetened condensed milk
Pour melted white chocolate mixture into bowl with cookie dough. Stir with spatula to combine.
Remove chocolate chips from freezer and mix into fudge. Pour fudge into prepared pan, spreading to all four corners. Place pan into refrigerator to set up for at least 2 hours. Cut into small squares before serving.