Preheat the oven to 350F. Line a 9x13 baking pan with parchment paper by buttering the bottom and sides, leaving an overhang on the two long sides. Set aside.

In a large bowl, whisk together the flour, salt, and cocoa powder and set aside.

Heat the chocolate, espresso powder, and butter in a double boiler or in a bowl over simmering water. Stir until completely melted. Turn off the heat and add the sugar, stirring until melted. Let it cool to room temperature.

Add the eggs and vanilla extract to the chocolate mixture and whisk until just incorporated.

Fold in the flour mixture with a spatula and mix until just combined. Do not overmix.

Fold in the peppermint baking chips, reserving about ¼ cup to sprinkle on top.

Transfer the batter to the baking pan and sprinkle the remaining chips on top.

Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with just a few crumbs.

Let the pan cool completely. Use a plastic knife around the edge of the pan to release any brownie stuck to the sides without parchment. Use the parchment paper flaps to lift the brownie slab out of the pan. Cut into pieces and serve.