In a 2-quart pot of boiling salted water, add the rice and cook until the grains begin to puff and break open, about 40 minutes to 1 hour. Drain and refresh in cold water. Season with salt and pepper.
Heat the oil in a 2-quart saucepan. Add the leek and cook for 1 minute. Add 3 tablespoons of the stock, the cranberries, and pears and cook, covered, stirring occasionally, until soft, about 8 minutes. Add the rice and remaining stock, raise the heat to high, and cook, stirring, 1 to 2 minutes. Season with salt and pepper and serve.