Blend flour, cornmeal, cumin, salt, milk, eggs, and 2 tablespoons butter in a blender until smooth. Let batter stand at room temperature 30 minutes. Lightly brush a 10-inch nonstick skillet with butter and heat over moderately high heat until hot but not smoking. Stir batter, then, holding skillet off heat, pour in 1/3 cup batter, immediately tilting and rotating skillet to coat bottom. (If batter sets before skillet is coated, reduce heat slightly for next crêpe.) Return skillet to heat and cook until just set and pale golden around edges, 10 to 15 seconds. Loosen edge of crêpe with a heatproof silicone spatula, then flip crêpe over carefully with your fingertips. Cook until underside is set, about 20 seconds more, and transfer crêpe to a plate. Make 11 more crêpes in same manner, brushing skillet lightly with butter for each and stacking crêpes on plate as cooked. Put oven rack in middle position and preheat oven to 375°F. Lightly butter a 13- by 9-inch (or 15- by 10-inch) shallow baking dish. Stir together ricotta, ham, egg, salt, and pepper. Put 1 crêpe, paler side up, on a work surface and spread 1 teaspoon pepper jelly in a horizontal line just below center of crêpe (toward end nearest you), leaving a 1-inch border on each side. Spoon 1/3 cup ricotta filling over jelly and fold in sides of crêpe over filling, then, beginning at bottom, roll up to enclose filling. Arrange crêpe, seam side down, in baking dish. Assemble 11 more crêpes in same manner, arranging them in 1 layer in baking dish. Bake, covered with foil, until filling is hot, about 30 minutes. Make topping just before serving:
Melt butter in 10-inch skillet over moderate heat until foam subsides, then cook white and pale green scallions, stirring, until softened, about 2 minutes. Add corn, salt, and pepper and cook, stirring, until crisp-tender, 2 to 3 minutes. Add scallion greens and cook, stirring, until softened, about 1 minute. Spoon topping over crêpes.
