Melt butter in a large saucepan over medium-high heat. Add onion to pan; sauté 5 minutes or until golden. Add rice to pan; sauté 1 minute. Add broth, 2 cups water, salt, and pepper to pan; bring to a boil. Cover, reduce heat, and cook 20 minutes, stirring occasionally. Stir in cheese, parsley, and peas; cook 2 minutes.