Preheat the oven to 350°F. Lightly grease a 9" x 13" pan

In a saucepan set over low heat, melt the butter, then add the sugar and stir to combine. Return the mixture to the heat briefly, just until it's hot, but not bubbling; it'll become shiny looking as you stir it. Heating this mixture a second time will dissolve more of the sugar, which will yield a shiny top crust on your brownies.

Transfer the sugar mixture to a medium-sized mixing bowl, if you've heated it in a saucepan. Stir in the cocoa, salt, baking powder, espresso powder, and vanilla.

Whisk in the eggs, stirring until smooth.

Add the flour and chips, again stirring until smooth.

Spoon 1/2 of the batter into a lightly greased 9" x 13" pan. Top with peppermint patties - be sure to place the candies as close together as possible to ensure each bite has a bit of candy in it. Spoon remaining batter on top of candy.

Bake the brownies for about 30 minutes, until a cake tester inserted into the center comes out clean, or with just a few moist crumbs clinging to it. The brownies should feel set on the edges, and the center should look very moist, but not uncooked. Remove them from the oven and cool completely prior to cutting.