Arroz Verde (Green Rice)

Put the cilantro, spinach, and broth in a blender and blend until the vegetables are pureed. Add the milk and salt and blend a bit more until well combined. In a medium (3 quart) heavy based saucepan with a lid, heat the butter and olive oil over medium heat. When the butter is melted, add the rice and saute, stirring about every 30 seconds, until it just begins to turn golden, 3 to 4 minutes. Add the onion and garlic and cook 1 minute, stirring constantly. Add the contents of the blender, stir well, turn the heat to high, and bring to a boil. Cover the pan, turn the heat to very low, and cook for 20 minutes. Stir the rice carefully to avoid crushing it, cover, and cook for another 5 minutes. Take the pan off the heat and let the rice steam in the covered pot for 10 minutes. Serve hot.