In a large saucepan over medium heat, melt the butter. Add the celery and shallot and sauté until the shallot is translucent, about 2 minutes. Add the rice and cook, stirring, until the grains are opaque, about 1 minute.
Cook the rice and peas
Raise the heat to medium-high, add the broth and 2cups (16fl oz/500ml) water, and bring to a boil. Reduce the heat to low, cover, and simmer until the rice is tender, about 20 minutes. Add the peas and cook, stirring occasionally, for 5 minutes longer. Just before serving, stir in the cheese and parsley and season with salt and pepper. Ladle into bowls and serve.