Grilled Chicken and Clam Paella

Name: Grilled Chicken and Clam Paella
Ingredients: 1 tablespoon olive oil; 1 medium leek, white and tender green, finely chopped; 2 garlic cloves, minced; 2 pounds skinless chicken breasts on the bone, cut crosswise into 2-inch pieces; Salt and freshly ground pepper; 2 cups medium-grain rice, such as Valencia; 1 1/4 cups fresh shelled fava beans (about 1 1/2 pounds in the shell) peeled, or fresh or frozen lima beans; 4 1/2 cups hot chicken stock or canned low-sodium broth; 1/4 teaspoon saffron threads; 2 large plum tomatoes, chopped; 2 fresh thyme sprigs; 1 fresh rosemary sprig; 2 pounds littleneck clams, scrubbed