Heat the extra-virgin olive oil in a sauce pot over medium heat. Add the orzo and toast until deeply golden, 4 to 5 minutes. Stir in the rice and toss with the orzo. Add the stock and bring to boil. Reduce the heat to a simmer, cover and cook 16 to 17 minutes until tender. Stir in the arugula and cheese and toss to combine. Transfer to a serving bowl and serve.