Photo: Jennifer Causey; Styling: Lindsey Lower
1. Bring cubed potato and water to cover to a simmer in small saucepan over medium-low. Cook until tender, about 10 minutes. Set aside. Cut kernels from 3 ears of the corn; reserve cobs. Preheat grill to medium (350°F to 400°F). Grill remaining 2 ears corn, covered, until charred, about 8 minutes, turning often. Cool 5 minutes; cut kernels from grilled corn, and discard grilled cobs.
2. Heat oil in a large saucepan over medium-high. Add onion, shallot, garlic, and sugar, and cook, stirring often, until tender and fragrant, about 5 minutes. Add butter and raw corn kernels, and cook until corn is tender, about 10 minutes. Stir in wine, and cook 1 minute.
3. Add cream, seafood stock, salt, cayenne pepper, reserved raw cobs, jalapeño halves, thyme sprigs, and rosemary sprig. Increase heat to high, and bring to a boil. Reduce heat to medium-low, and cook until liquid is reduced by one-third, 15 to 20 minutes. Remove and discard thyme, rosemary, corn cobs, and jalapeño halves.
4. Transfer mixture to a blender. Remove center piece of blender lid (to allow steam to escape); secure lid on blender, and place a clean towel over opening in lid. Process mixture until smooth, about 30 seconds. Return mixture to saucepan. Stir in grilled corn kernels, cooked clam meat, cooked potatoes, and uncooked clams in shells. Cover and cook over medium-low until clamshells open, about 5 minutes. Remove opened clams; divide among 4 bowls.
5. Ladle chowder over clams, and sprinkle with herbs. Serve with lemon wedges.