Preheat the oven to 350 degrees F. Spray a 9x13 pan with nonstick spray or line with parchment paper.
Mix together melted butter, sugar, and peppermint extract until fully combined then add in eggs one at a time, making sure to fully incorporate each one.
Stir in cocoa powder, flour, and salt until just combined. Fold in chocolate. chips.
Transfer brownie batter into the greased/lined pan and bake uncovered for 20-22 minutes until a toothpick inserted into the center comes out slightly wet.
While the brownies are cooking, cut the York peppermint patties into fourths.
Remove the brownies from the oven and carefully place the peppermint patties all over the top. Return to the oven for 8-10 minutes just until the peppermint patties are melted.
Remove the brownies from the oven and immediately spread the melted peppermint patties with a spatula.
Cool completely then frost the brownies with the chocolate frosting.