Combine soup, milk, mustard and tarragon. Stir in chicken, broccoli and green onion. Spoon about 1/2 cup mixture into centre of each tortilla. Fold in sides and roll up. Place, seam side down, in greased 12x8x1 3/4-inch (30x20x4.5cm) baking dish. Bake at 350F(180 °C) for 15 minutes. Sprinkle with cheese. Bake 10 minutes longer.