How to Make It
In a bowl, whisk the eggs. Whisk in the milk, flour, masa harina, sugar and salt until blended. Let the batter stand for 30 minutes.
In a saucepan, cover the potato with water, add a pinch of salt and bring to a boil. Simmer over moderately high heat until tender, about 8 minutes. Drain in a colander and return to the saucepan. Shake the pan over high heat to dry the potato, about 20 seconds; transfer to a microwave-safe bowl and mash until it's slightly chunky. Stir in the 1/2 cup of cream.
In a medium skillet, melt the butter. Add the onion and jalapeño and cook over moderate heat until softened, about 5 minutes. Add the corn, cover and cook, stirring a few times, until the corn is tender, about 6 minutes. Stir in the scallions. Stir the corn mixture into the mashed potatoes and season with salt and pepper.
Heat an 8-inch nonstick skillet and rub it with vegetable oil. When the pan is hot, add 2 tablespoons of the crêpe batter, swirl to coat the bottom and cook over moderately high heat until lightly browned on the bottom, about 1 1/2 minutes. Carefully turn the crêpe over and continue cooking until brown in spots, about 1 minute longer. Transfer to a baking sheet and repeat to make 7 more crêpes.
Preheat the broiler. Reheat the potato-corn filling in a microwave oven for 45 seconds. Spoon 2 tablespoons of the filling onto one side of each crêpe and fold the crêpes in half. Transfer the crêpes to a baking sheet and brush the tops with cream. Broil until browned on top, about 10 seconds. Place the crêpes on plates, sprinkle with the cheese and serve.
Instant masa harina, like regular masa harina, is made from corn treated with limewater. It can be found in the Latin section of most supermarkets. Do not substitute other types of cornmeal.