01 -
Place potatoes in a large saucepan; add water to cover. Bring to a boil. Reduce heat and cook, uncovered, for 5 minutes. Drain potatoes and toss with 1 tablespoon oil.
02 -
Grill poblanos, covered, over high heat until skins are blistered and blackened on all sides, 8-10 minutes, turning occasionally. Immediately place peppers in a small bowl, cover, and let stand for 20 minutes. Reduce grill temperature to medium heat.
03 -
Meanwhile, brush corn with remaining 1 tablespoon oil. Place potatoes in a grill basket. Grill corn and potatoes, covered, over medium heat until tender and lightly browned, 12-15 minutes, turning occasionally. Cool slightly.
04 -
Grill green onions until blackened, 5-6 minutes. Cut into 1-inch pieces and place in a large bowl. Peel off and discard charred skin from poblanos. Remove stems and seeds. Cut peppers into 1/2-inch pieces and add to onions. Cut corn from cobs; add corn and potatoes to peppers.
05 -
In a small bowl, whisk together sour cream, mayonnaise, and lime juice until blended. Stir in cheese, cilantro, lime zest, salt, and pepper.
06 -
Add the dressing to the potato mixture and stir to coat. Refrigerate, covered, for at least 1 hour before serving. If desired, top with additional Cotija cheese or cilantro and serve with lime wedges.