To prepare dressing, combine first 8 ingredients in a large bowl; stir well with a whisk. Set aside.
To prepare shrimp, combine 2 teaspoons olive oil and next 6 ingredients (through shrimp) in a large bowl; toss well. Thread about 5 shrimp onto each of 6 (8-inch) skewers. Place skewers on a grill rack coated with cooking spray; grill 3 minutes or until done.
To prepare salad, add spinach, mushrooms, and onion to vinegar mixture; toss gently to coat. Serve with shrimp skewers.
So tasty, so simple. Doubled the dressing and made half the shrimp for a dinner sized salad for my husband and I. Doubling dressing wasn't necessary, halving the shrimp made for perfect portions (along with halved salad ingredients plus a handful more of spinach). I really dislike cumin but it gave the shrimp a nice smokey texture. Agree that you could add something like pecans to make it more crunchy or filling but not sure you need it. Delicious, will be making it again and again.