Cream Cheese Brownies

1. FOR THE BROWNIE BASE: Adjust oven rack to lower-middle position and heat oven to 325 degrees. Make foil sling by folding 2 long sheets of aluminum foil so that they are as wide as 8-inch square baking pan. Lay sheets of foil in pan perpendicular to one another, with extra foil hanging over edges of pan. Push foil into corners and up sides of pan, smoothing foil flush to pan. Grease foil and set aside. Whisk flour, salt, and baking powder in small bowl until combined; set aside.
2. Melt chocolate and butter in medium heatproof bowl set over pan of almost-simmering water, stirring occasionally, until mixture is smooth. Remove melted chocolate mixture from heat; whisk in sugar and vanilla; then whisk in eggs, one at time, fully incorporating each before adding next. Continue whisking until mixture is completely smooth. Add dry ingredients; whisk until just incorporated.
3. FOR THE CREAM CHEESE FILLING: Beat cream cheese in small bowl with sugar, vanilla, and egg yolk until combined.
4. Transfer half of brownie batter into prepared pan. Drop half of cream cheese mixture, by spoonfuls, over batter. Repeat layering with remaining brownie batter and cream cheese filling. Using tip of butter knife, gently swirl batter and cream cheese filling.
5. Bake until edges of brownies have puffed slightly, center feels not quite firm when touched lightly, and toothpick inserted in center comes out with several moist crumbs attached, 50 to 60 minutes, rotating pan halfway through baking.
6. Let brownies cool in pan on wire rack for 5 minutes. Remove brownies from pan using foil. Let brownies cool on wire rack to room temperature, about 1-1⁄2 hours. Refrigerate until chilled, at least 3 hours. (To hasten chilling, place brownies in freezer for about 1-1⁄2 hours.) Cut brownies into 2-inch squares and serve. (Don’t cut brownies until ready to serve. Brownies can be wrapped in plastic wrap and refrigerated for up to 3 days.)

MAKING CREAM CHEESE BROWNIES
1. Pour half of brownie batter into prepared pan; then drop half of cream cheese mixture, by spoonfuls, over batter.
2. Repeat with remaining batter and cream cheese mixture. Use a knife or spoon handle to gently swirl the batter and cream cheese filling.