FOR THE BROWNIES: – 4 ounces (113g) bittersweet chocolate (about 70% cacao) discs or bar (roughly chopped) – 3/4 cup (170g) unsalted butter – 1 & 1/4 cups (250g) granulated sugar – 1/2 cup (50g) firmly packed light brown sugar – 3 large egg – 1 teaspoon vanilla extract – 1/4 teaspoon salt – 1 cup (120g) all-purpose flour FOR THE CHEESECAKE SWIRL: – 4 ounces (113g) cream cheese, at room temperature – 2 tablespoons granulated sugar – 1/8 teaspoon vanilla extract – 1/2 large egg* – 3 tablespoons cookie butter**