Line an 8x8-inch baking pan with parchment paper, allowing some overhang on the sides. This makes lifting the fudge out super easy later!
In a medium saucepan, combine your white chocolate chips, light condensed milk, and softened butter. Heat this mixture over low heat, stirring constantly, until it's completely smooth and wonderfully melted (this usually takes about 4-5 minutes). Patience is key here to avoid scorching!
Remove the saucepan from the heat. Stir in the peppermint extract, the optional green food coloring (add a drop at a time until you get your desired jolly shade!), and the pinch of sea salt. Mix until everything is beautifully combined and the fudge is a lovely pastel green.
Gently fold about half of your roughly chopped sandwich cookies into the fudge mixture. This ensures you get delightful crunchy bits throughout your sweet treat.
Pour the fudge mixture into your prepared pan and use a spatula or the back of a spoon to spread it evenly. Sprinkle the remaining chopped cookies over the top and gently press them down a little, just enough to adhere.
Pop the pan into the refrigerator for at least 45 minutes, or until the fudge is firm to the touch. For the best, firmest results, chilling it overnight is ideal.
Once firm, use the parchment paper overhang to easily lift the entire slab of fudge out of the pan. With a sharp knife (warming the blade under hot water briefly before each cut can help make them extra clean!), slice the fudge into 1-inch squares. Now, enjoy your easy, festive, and slightly healthier holiday creation!