Preheat your oven to 350°F (175°C). In a large mixing bowl, cream together the softened unsalted butter and brown sugar until light and fluffy. This should take about 2-3 minutes.
To the creamed mixture, add the all-purpose flour and salt. Mix until just combined, ensuring not to over-mix.
Take about two-thirds of the crumb mixture and press it evenly into the bottom of a greased 9x13 inch baking pan. This will be your base.
In a medium saucepan over low heat, melt the bittersweet chocolate chips with the sweetened condensed milk, stirring constantly until smooth.
Once melted, pour the chocolate fudge mixture over the prepared crust in the baking pan, spreading it evenly.
Sprinkle the Andes Creme de Menthe Chocolate Mint Baking Chips and the semi-sweet chocolate chips over the fudge layer, ensuring an even distribution.
Take the remaining crumb mixture and crumble it over the top of the fudge and mint chips. This creates a beautiful top layer for your bars.
Bake in the preheated oven for about 25-30 minutes, or until the top is golden brown and the fudge is bubbly.
Remove from the oven and allow to cool in the pan for at least 30 minutes. Once cooled, cut into squares and enjoy!
