Preparation Char chilies over gas flame or in broiler until blackened on all sides. Enclose in paper bag; let stand 10 minutes. Peel and seed chilies. Cut chilies into 1/2-inch pieces. Transfer to large bowl. Place potatoes on steamer rack set over boiling water in pot. Cover and steam until potatoes are just tender, about 10 minutes. Cool. Transfer to bowl with chilies. Mix in tomatillos, green onions and chopped cilantro. Whisk sour cream, lime juice and cumin in small bowl to blend. Add to potato mixture and toss to coat. Season generously with salt and pepper. (Can be prepared 6 hours ahead. Cover and refrigerate. Let stand at room temperature 30 minutes before serving.) Mound potato salad on platter. Garnish with cilantro sprigs and serve.
Preparation Char chilies over gas flame or in broiler until blackened on all sides. Enclose in paper bag; let stand 10 minutes. Peel and seed chilies. Cut chilies into 1/2-inch pieces. Transfer to large bowl. Place potatoes on steamer rack set over boiling water in pot. Cover and steam until potatoes are just tender, about 10 minutes. Cool. Transfer to bowl with chilies. Mix in tomatillos, green onions and chopped cilantro. Whisk sour cream, lime juice and cumin in small bowl to blend. Add to potato mixture and toss to coat. Season generously with salt and pepper. (Can be prepared 6 hours ahead. Cover and refrigerate. Let stand at room temperature 30 minutes before serving.) Mound potato salad on platter. Garnish with cilantro sprigs and serve.