Place an oven rack in the top one-third of the oven and preheat oven to 425°F. Cut four 24x15-inch sheets of parchment paper. Fold each sheet in half, forming 15x12-inch rectangles. Cut a heart shape from one of the rectangles. Use this as a guide to cut 3 more hearts from the remaining rectangles. Set hearts aside.
In a small bowl combine 2 teaspoons ginger with 1 tablespoon water. In a large bowl combine the broccoli slaw and the ginger mixture and toss to coat.
Working with one at a time, unfold the parchment and mound 1/4 of the broccoli slaw (about 1 1/2 cups) on one side of the heart, leaving a 3-inch border. Place the salmon on the mounds, tucking under any thin edges. Starting at the top of the heart, make a 1/2-inch folded edge, creasing crisply. Working your way around again, make overlapping 1/2-inch folds. Twist the tip of the heart and tuck it under the packet. Place packets on a large baking sheet (they may overlap). Bake for 12 to 15 minutes or until salmon flakes easily when tested with a fork.
Meanwhile, in a small saucepan combine the chicken broth, mirin, tamari sauce, brown sugar, remaining ginger, and cornstarch. Cook and stir over medium heat until thickened and bubbly. Cook and stir 2 minutes more. Spoon the sauce over salmon and slaw before serving.