Preheat the oven to 350-degrees. Line a 13x9 baking pan with parchment paper or aluminum foil and apply nonstick spray.
In a food processor or mixer, add the flour, cocoa, sugar, butter and egg. Mix for a few minutes, until it resembles coarse crumbs. Scoop out 3/4 cup and it aside.
Take the rest of the cookie dough out and press it into the prepared pan. Bake for 10 minutes.
Meanwhile, melt the 1 cup of dark chocolate (microwave or stovetop), then mix it with the can of condensed milk and the reserved cookie dough. This creates a thick, muddy batter.
Remove the partially-baked crust from the oven and gently spread the chocolate mix over it as evenly as possible. Sprinkle the mint chips and chopped York patties over the top.
Bake for another 25 minutes. Let it cool completely in the pan before using the parchment/foil to lift it out of dish for easier cutting.
OM NOM NOM!