Combine butter and garlic and set aside. Heat oil in a large pot over high heat, add popcorn, and cover. Shake pot often as corn pops. When popping slows to a few seconds between pops, remove from heat and let sit until popping stops. Transfer to a large bowl and drizzle with garlic butter. Toss well to coat evenly. Sprinkle with parmesan, parsley, and salt to taste; toss again.