PreparationMake chipotle mayonnaise: Whisk together mayonnaise, chipotle, and lemon juice and chill mixture, its surface covered with plastic wrap. Fry oysters: Heat oil in a deep heavy pot (preferably a cast-iron Dutch oven) over high heat until it registers 375°F on deep-fat thermometer, about 12 minutes. While oil is heating, whisk together egg, milk, and 1 teaspoon salt in a bowl. Shake cornmeal, remaining 1 1/2 teaspoons salt, and pepper in a plastic or paper bag until combined well. Working in batches, add oysters to egg mixture, then lift out, letting excess drip off, and transfer to cornmeal in bag, shaking to coat well. Carefully transfer to oil, knocking off excess coating, and fry, turning occasionally, until golden and just cooked through, 1 to 2 minutes. Transfer with a slotted spoon to paper towels to drain. Coat and fry remaining oysters in same manner, returning oil to 375°F for each batch. Assemble sandwich: Halve loaf crosswise and horizontally, cutting all the way through, and spread one cut side of each piece with mayonnaise. Sandwich oysters and lettuce between bread, pressing gently.
PreparationMake chipotle mayonnaise: Whisk together mayonnaise, chipotle, and lemon juice and chill mixture, its surface covered with plastic wrap. Fry oysters: Heat oil in a deep heavy pot (preferably a cast-iron Dutch oven) over high heat until it registers 375°F on deep-fat thermometer, about 12 minutes. While oil is heating, whisk together egg, milk, and 1 teaspoon salt in a bowl. Shake cornmeal, remaining 1 1/2 teaspoons salt, and pepper in a plastic or paper bag until combined well. Working in batches, add oysters to egg mixture, then lift out, letting excess drip off, and transfer to cornmeal in bag, shaking to coat well. Carefully transfer to oil, knocking off excess coating, and fry, turning occasionally, until golden and just cooked through, 1 to 2 minutes. Transfer with a slotted spoon to paper towels to drain. Coat and fry remaining oysters in same manner, returning oil to 375°F for each batch. Assemble sandwich: Halve loaf crosswise and horizontally, cutting all the way through, and spread one cut side of each piece with mayonnaise. Sandwich oysters and lettuce between bread, pressing gently.