12 brownie cupcakes or 24 two-inch square brownies
Ingredients
1 cup all-purpose flour
1 teaspoon baking powder
¼ teaspoon espresso powder
1 pound 70 percent cacao chocolate, chopped
2½ cups sugar
¾ cup unsalted butter
1 teaspoon vanilla extract
½ teaspoon kosher salt
5 large eggs, at room temperature
Sifted cocoa, for dusting
Directions
Butter 12 standard cupcake cups or one 9-by-13-inch baking pan and dust with sifted cocoa. Tap out the excess cocoa.
Preheat the oven to 350º.
Sift together the flour, baking powder and espresso powder into a bowl. Set aside.
In a large microwave-safe bowl, combine the chocolate, sugar, butter, vanilla and salt. Microwave on high for 1 minute, then stir. Continue to microwave for 1-minute intervals until the chocolate is completely melted. (Alternatively, melt chocolate on a double boiler or bain-marie.) 5. While still warm, transfer the chocolate mixture to the bowl of a stand mixer fitted with a paddle attachment. Mix on low for 30 seconds, then add the eggs, one at a time, beating after each addition until well combined and shiny. Add the flour mixture and beat until just combined. Raise the speed to medium and beat for another 30 seconds until the batter is shiny. It will be very liquid.
Scoop the batter into the prepared pan. If it is still warm, it should flow to the edges. If it has cooled, just use your offset spatula to smooth it into place. If using the walnuts, dot them on each cupcake or sprinkle them evenly over the pan and lightly press them onto the batter. Bake the brownies until they begin to pull away from the sides of the pan and a tester inserted in the center comes out clean, 18 to 20 minutes for cupcakes or 40 to 45 minutes for the 9-by-13-inch pan.
Remove from the oven and immediately transfer the cupcakes from the pan to wire racks to cool. If using the baking pan, let the brownies cool in the pan for about 20 minutes, then cut them while still a tad warm into roughly 2-inch squares. Store in airtight containers for up to 1 week.