3 1/2 ounces unsweetened chocolate (I used 4 ounces)
10 tablespoons (1 1/4 sticks) unsalted butter
1 cup sugar
3 large eggs
1/2 cup all-purpose flour
1 pound cream cheese
1/2 cup sugar
1 large egg
1 large egg yolk
1 1/2 teaspoons fresh lemon juice
1/2 cup to 3/4 cup mini chocolate chips, optional
- Preheat the oven to 300 degrees F. Line a 9-inch square pan with foil and lightly spray with nonstick cooking spray.
- Prepare the brownie: Melt the chocolate and butter together in the top of a double boiler placed over simmering water. Whisk until smooth and combined. Let mixture cool for 5 minutes.
- Place the sugar and eggs in a mixing bowl and beat on medium-high speed until pale yellow, 2 minutes. Scrape the bowl with a rubber spatula.
- Add the flour on low speed and mix for 5 seconds. Scrape the bowl.
- Add the cooled chocolate mixture on low speed and blend until mixed, 15 seconds, stopping the mixer once to scrape the bowl. Do not overmix.
- Spread the batter evenly in the prepared pan and place the pan in the freezer for 10 minutes. Do not skip this step.
- Meanwhile, prepare the cheesecake topping: Place all the cheesecake ingredients except mini chocolate chips in a food processor and process until smooth, 1 minute. Stop the machine once during the process to scrape the bowl. Add mini chocolate chips, if using.
- Remove the pan from the freezer. Carefully spoon the cheesecake mixture over the brownie layer, and, using a spatula, spread it over the brownie in an even layer, being careful not to mix the two layers together.
- Bake on the center rack of the oven until the top is set and the center is just about level with the edges, 1 hour and 5 to 10 minutes.
- Cool the brownies in the pan for 30 minutes. Lift out of the pan using the foil ends. Let cool completely before cutting into squares with a sharp knife. Wipe the knife between cuts with a damp paper towel. If not consuming immediately, cover tightly with plastic wrap and refrigerate or freeze.