Coat cold cooking grate of grill with cooking spray, and place on grill. Preheat grill to 350° to 400° (medium-high) heat.
Peel sweet potatoes, and cut into 1/2-inch-thick rounds. Bring potatoes and water to cover to a boil in a large Dutch oven over medium-high heat; cook 5 to 6 minutes or until crisp-tender. Drain. Coat potatoes with cooking spray.
Grill potatoes, covered with grill lid, 8 to 10 minutes or until tender, turning occasionally. Gently toss warm potatoes with poblano and Cilantro Vinaigrette. Arrange mâche on a serving platter, and sprinkle with queso fresco and cranberries. Top with sweet potato mixture, and sprinkle with pumpkin seeds.