Thai Corn Chowder

Name: Thai Corn Chowder
Ingredients: 4 ears corn; 2 cups diced red-skinned potatoes (about 12 ounces); 3/4 cup chopped scallions; 2 tablespoons grated peeled fresh ginger; 4 cloves garlic, smashed; 8 black peppercorns; 1 stalk lemongrass, cut into thirds (optional); 4 tablespoons unsalted butter; Kosher salt; 1 red jalapeno pepper, seeded and minced; 1 13 .5-ounce can coconut milk; 8 fresh basil leaves; 8 fresh mint leaves; 4 radishes, thinly sliced; 1/4 cup roughly chopped fresh cilantro; Juice of 1/2 lime, plus lime wedges for garnish; 1 tomato, seeded and diced