How to Make It
Prepare the Brownie: Preheat oven to 350°F. Spray a 9-inch square baking pan with cooking spray. Fold 2 (16-inch) pieces of aluminum foil lengthwise to measure 8-inches wide. Fit 1 sheet in the bottom of greased baking pan, pushing foil into corners and up sides of pan, allowing excess foil to hang over sides. Fit second sheet in pan, the opposite way, fitting into corners and up sides; allowing excess to hang over sides. Lightly spray foil with cooking spray to cover bottom and sides of pan.
Whisk together sugar, flour, cocoa, and salt in a medium bowl until combined. Whisk together eggs, oil, and vanilla in a small bowl until combined. Gently stir egg mixture into flour mixture, folding until just combined. Fold in chopped chocolate mint candies. Spoon into prepared pan, spreading in an even layer.
Prepare the Cheesecake: Beat together cream cheese, sugar, vanilla, peppermint extract, and egg yolk in a medium bowl with an electric mixer on medium speed until creamy, 1 to 2 minutes. Add food coloring by the drop until desired color of green is achieved, stirring to blend.
Drop Cheesecake mixture by spoonfuls, over Brownie batter. Use a butter knife or wooden pick to gently swirl batter layers to create a swirled, marbled pattern. Bake in preheated oven until a wooden pick inserted in center comes out with a few wet crumbs, about 30 minutes. Let cool on a wire rack in pan about 1 hour. Cut into 9 brownies.