1. Fill a large pot half-full with water, and bring to a boil.
2. Meanwhile, combine the dressing ingredients in a blender and process until smooth, about 20-30 seconds. Set aside.
3. When water is boiling, add shrimp and asparagus pieces; cook 3-4 minutes or until shrimp is cooked through and asparagus is bright green. Drain in a colander, and run cold water over the shrimp and asparagus. When cool, toss the shrimp and asparagus with bell pepper, cucumber, and avocado in mixing bowl. Pour dressing over shrimp-and-vegetable mixture, and toss to coat.
4. Divide greens among 4 plates, and top each with 1/4 of the shrimp-and-vegetable mixture.