Heat oil in a frying pan or skillet over medium-high heat. Once the oil is hot, add corn kernels. Cook until the corn kernels are slightly charred on all sides (toss as needed) and heated through, about six minutes. Transfer corn kernels to a mixing bowl and allow to cool for two to three minutes, then add mayonnaise, green chiles, lime zest, cheese, green onion, cilantro, and salt. Use a spatula to gently but thoroughly combine. Set aside.
Brush more mayonnaise on the outer sides of each of the corn sourdough slices. In the same frying pan or skillet used to char the corn, add two slices (mayonnaise side down) over medium heat. Add a generous amount of the corn and cheese mixture on top of each slice, then top each with another slice (mayonnaise side up). Once toasted and golden, use a large spatula to carefully flip the sandwiches to toast the other side. Monitor the heat of the pan or skillet to ensure toasting is happening evenly and slowly, which will allow the cheese in the filling to melt through. Once ready, transfer to a cutting board and use a serrated knife to slice in halves and enjoy immediately.