In a large, heavy pot, combine 3 tablespoons vegetable oil and 1/2 cup popcorn kernels. Cover and cook over high heat, shaking the pot often, until the popping stops, 3 to 5 minutes. Add 6 tablespoons melted butter and toss. Dump the popcorn into a large paper bag and toss with 1 cup grated pecorino-romano cheese and 1 teaspoon coarsely ground pepper.
