Add the garlic to the vegetable broth along with the saffron, if using, the pepper, cloves, sage, thyme, and oil. Stir in the rice kernels. Bring to a gentle boil, cover, reduce the heat and simmer for about one hour. While the soup is simmering, melt the butter in a skillet. On very low heat cook and stir the onions until they are very soft and translucent. Stir the sautéed onions into the broth. Taste and adjust seasoning, adding more salt if needed.