1. Preheat oven to 350ºF. Line a 9-by-13-inch baking dish with foil, leaving a 2-inch overhang on each short side. Mist with cooking spray.
2. In a large pan over low heat, melt butter and semisweet chocolate, stirring often. Transfer to a bowl and let cool for 10 minutes. Whisk in sugar, eggs and vanilla, then stir in flour and salt until just combined. Fold in chocolate chips. Pour batter into baking dish. Spoon jam into a small bowl and stir vigorously to loosen. Drizzle jam evenly over batter and swirl in lightly with a spoon. Bake until the top has set and a toothpick inserted in center comes out clean, about 40 minutes. Let cool in pan on a wire rack.
3. When completely cooled, run a knife around edges without foil. Using foil handles, lift brownies out of pan, place on a cutting board and peel off foil. Cut into 24 squares, then cut squares in half on the diagonal. Store in an airtight container at room temperature.