The Best Brownie Ever (Kopie)

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1 cup (2 sticks) unsalted butter
2 1/4 cups granulated sugar
4 large eggs
1 1/4 cup Dutch-process cocoa
1 teaspoon salt
1 teaspoon baking powder
1 teaspoon espresso powder
1 tablespoon vanilla extract
1 1/2 cups all-purpose flour
2 cups chocolate chips (I used Ghirardelli 60% Cacao -- my favorite for baking)

Preheat oven to 350 degrees F. Generously butter a 9x13 inch pan.
In a large-sized microwave-safe bowl, melt the butter, then add the sugar and stir to combine. Return the mixture to the microwave briefly, just until it's hot, but not bubbling; it'll become shiny looking as you stir it. Heating the butter and sugar a second time will dissolve more of the sugar, which will yield a shiny top crust on your brownie.
Stir in the cocoa, salt, baking powder, and vanilla. Add the eggs, beating until smooth; then stir in the flour until combined. Feel free to add the chocolate chips now if you want a smoother texture (no chocolate chunks), but keep in mind that if you wait just 20 minutes, or so -- the chocolate chips will remain intact. I prefer to have a nice chunk of chocolate to bite into. Spoon the batter into a prepared pan.
Bake the brownies for 28-30 minutes, until a cake tester inserted into the center comes out dry (though it may have a few crumbs clinging to it). The brownies should feel set both on the edges and in the center. Remove them from the oven, and after 5 minutes loosen the edges with a butter knife; this helps prevent the brownies from sinking in the center as they cool. Cool completely before cutting and serving.

Source: Adapted from King Arthur Flour