A bite of this flan, fragrant with traditional pumpkin-pie spices, is very comforting despite the dessert's modern looks; a topping of pumpkin seeds, seasoned with cayenne, creates a play of sweet and heat.
03Bring cream and milk to a bare simmer in a 2-quart heavy saucepan over moderate heat, then remove from heat. Whisk together whole eggs, yolk, and remaining cup sugar in a large bowl until combined well, then whisk in pumpkin, vanilla, spices, and salt until combined well. Add hot cream mixture in a slow stream, whisking.
04Pour custard through a fine-mesh sieve into a bowl, scraping with a rubber spatula to force through, and stir to combine well. Pour custard over caramel in dish, then bake in a water bath until flan is golden brown on top and a knife inserted in center comes out clean, about 1 1/4 hours. Remove dish from water bath and transfer to a rack to cool. Chill flan, covered, until cold, at least 6 hours.
05Toast pumpkin seeds in oil in a 10- to 12-inch heavy skillet (preferably cast-iron) over moderately low heat, stirring constantly, until puffed and golden, 8 to 10 minutes. Toss with salt and cayenne until coated.
06Run a thin knife between flan and side of dish to loosen. Shake dish gently from side to side and, when flan moves freely in dish, invert a large platter with a lip over dish. Holding dish and platter securely together, quickly invert and turn out flan onto platter. (Caramel will pour out over and around flan.) Sprinkle flan with spiced pumpkin seeds just before serving.