The gizzard is an muscular organ found in the digestive tract of poultry. Since birds don't have teeth to grind their food, the gizzard helps them to grind their food before digesting it. Gizzards are used in many different cuisines from China where it is stir-fried to the southern U.S., where it is braised or fried. In Portugal, gizzards are served in thick stew called moelas. Because they are made of tough muscle and connective tissue, gizzards need to be cooked a long time to make them tender.
Rinse the gizzards. Peel off the inner skin if it hasn't already been done. It is olive-green in color and peels off easily. Left in place, it makes the gizzards taste bitter.
Heat the oil in a frying pan over medium heat. Add the garlic, onion and bay leaf. Saute them for a few minutes until the onions soften and begin to look glazed.
Put the onion mixture and the gizzards in the slow cooker. Add the chicken broth, tomatoes and herbs. If necessary, add enough water to barely cover the gizzards. Cover the slow cooker and cook on low for four hours.
Remove the gizzards from the slow cooker. Taste the broth for seasoning and add salt if necessary. Measure the broth. Add 1 cup of rice for every 2 cups of broth. Return the gizzards to the slow cooker with the rice. Cover and cook another two hours until the rice has absorbed all the liquid and the gizzards and rice are fully cooked.