Combine 1/4 cup balsamic vinegar, 2 teaspoons honey and a bay leaf in a saucepan over medium-high heat; cook until syrupy, 5 minutes. Melt 6 tablespoons butter in a large skillet over medium heat, then add 1/3 cup sage leaves and 1 cup chopped walnuts; cook 3 minutes. Add 1 cup pasta-cooking water and cook until reduced by half, 2 minutes. Toss with 1 pound cooked tortellini, some grated parmesan and salt. Drizzle with the balsamic syrup.