12 ounces fine-quality semisweet chocolate
1/2 pound (2 sticks) unsalted butter, at room temperature
1 1/3 cups granulated sugar
6 eggs
1 cup cake flour
1/4 cup espresso powder or instant coffee powder
2 (8 ounce) containers mascarpone cheese
1/4 cup granulated sugar
2 eggs
2 teaspoons vanilla extract
1 teaspoon cocoa powder

Line a 9 x 13-inch baking pan with parchment or wax paper. Butter and flour parchment and sides of pan.

Chop or break chocolate into small pieces. Melt in a microwave or in a heavy-bottomed saucepan over low heat. Stir until smooth. Pour into mixer bowl. Cool slightly, until just warm to the touch.

Beat butter into warm chocolate. Beat in 1 1/3 cups sugar. Add eggs one at a time, beating until mixture lightens.

Combine cake flour and espresso powder. Blend in flour mixture on low speed. Do not overmix. Pour into pan.

In a medium bowl, whisk together cheese, 1/4 cup sugar, eggs and vanilla extract. Pour over brownie batter in pan. Bake at 350 degrees F for 35 to 40 minutes, until middle is almost set and top begins to crack.

Cool in pan. Remove brownie from pan, peel off paper and dust lightly with cocoa powder. Cut into 40 small bars.