Prepare Mustard-Herb Dressing.
In a saucepan, cook asparagus, covered, in a small amount of boiling salted water for about 4 minutes or until crisp-tender. (Or steam asparagus for about 4 minutes.) Immediately drain and plunge into ice water. Drain.
In a saucepan, cook squash, covered, in a small amount of boiling salted water for about 3 minutes or until crisp-tender. (Or steam squash for about 3 minutes.) Immediately drain and plunge into ice water. Drain.
In a salad bowl, combine the baby salad greens or other greens, asparagus, and yellow squash. Sprinkle with sunflower seeds. Toss with Mustard-Herb Dressing to coat. Makes 8 side-dish servings.