NOTES: You can grill the corn a day ahead of using it; cover and chill. Or, instead of grilling the corn, you can broil it 4 inches from heat, turning several times, until lightly browned all over, about 10 minutes. You can make the mashed potatoes up to 2 days ahead; cover and chill, then reheat in a microwave oven on full power (100%), stirring occasionally, until heated through, 10 to 15 minutes.
4 ears corn, husks and silks removed
About 2 tsp. vegetable oil
5 pounds russet potatoes, peeled and cut into 2-inch chunks
1/4 cup (1/8 lb.) butter
About 3/4 cup whole milk, heated
About 2 drained canned chipotle chiles, minced
Salt and fresh-ground pepper
How to Make It
Lightly rub corn with oil. Lay corn on a barbecue grill over a solid bed of medium-hot coals or medium-high heat on a gas grill (you can hold your hand at grill level only 3 to 4 seconds); close lid on gas grill. Cook, turning often, until corn kernels are lightly browned all over, with some blackened spots, 5 to 7 minutes (see notes). Let stand until cool enough to handle, then, holding corn upright in a deep bowl, cut kernels from ears with a sharp knife.
Meanwhile, in a 5- to 6-quart pan over high heat, bring 3 quarts water to a boil. Add potatoes and cook until very tender when pierced, about 20 minutes. Drain and return to pan.
Add butter and 3/4 cup milk and beat with an electric mixer on medium speed, or mash with a potato masher, until smooth. Beat or stir in roasted corn and chipotles to taste. If potatoes are stiffer than you like, beat in a little more milk. Add salt and pepper to taste. Spoon into a serving bowl.