Combine onion, garlic, parsley and basil in a food processor and puree. Put oil in a 6 or 8-cup saucepan with a lid over medium heat. A minute later, add the rice and cook, stirring occasionally, until it glistens, just a few minutes. Stir in all but a tablespoon of the onion mixture with salt and pepper and cook for a couple of minutes, stirring. Add the chicken stock, bring to a boil and cover. Turn the heat to medium-low and cook until the liquid is absorbed, 15 to 20 minutes. Stir in the reserved onion mixture and serve immediately.