Combine kernels and oil in a heavy 3-qt. saucepan. Cover with lid, and cook over medium heat 2 to 3 minutes or until kernels begin to pop. Cook, shaking pan often, 2 more minutes or until popping slows. Transfer popcorn to a serving bowl. Drizzle with butter, and sprinkle warm popcorn with kosher salt and pepper; toss to coat.