Line 8x8 pan with foil and spray with non-stick spray.
Melt white chips and shortening by microwaving for 45 seconds, stirring and repeating until melted and smooth.
Add sweetened condensed milk and mint to melted chocolate and stir to incorporate.
Add food colouring to reach desired colour.
Allow mixture to cool a little before adding mini chips or they will melt.
Fold in mini chips, reserving about 1/4 to place on top.
Transfer to prepared pan and press into place.
Sprinkle top with reserved chips and refrigerate for at least 1 hour before cutting.