Line an 8×8 square pan with foil and lightly spray with cooking spray. Set aside.
In a microwave safe bowl, microwave white chocolate chips and butter on high for 1 minute. Let rest for 1 minute then check to see if melted. If needed microwave for another 30-45 seconds. Stir chocolate until all lumps are gone.
Stir in sweetened condensed milk and mint extract. Add food colouring to desired colour.
Once completely incorporated, let cool for a few minutes then fold in 1/2 cup mini chocolate chips.
Press fudge into prepared pan. Sprinkle remaining mini chocolate chips on top and gently press into fudge.
Refrigerate for a minimum of 2 hours to set before cutting into squares.