Put the lentils, water, bay leaf, sage, and oregano or marjoram in a soup pot. Bring to a boil, reduce heat, and simmer for about 20 minutes, or until the lentils are tender. Remove the bay leaf.
While the lentils are cooking, preheat the oven to 350 degrees. Wrap the head of garlic in foil or place it on a baking sheet and roast for 30 minutes. After it has cooled, squeeze the garlic out of the skin and into a food processor or blender. Puree with the tomatoes and juice. Set aside.
Put the 1/4 cup water in a skillet or large saucepan and turn the heat to medium. Add the onion, cumin, and oregano and cook until soft. Add the carrot and red pepper and cook until tender. Add the chile puree, the potatoes, and the tomato-garlic mixture and cook for 10 minutes at medium-low heat.
Combine the lentils and liquid with the vegetables. Cook over low heat for 30 minutes, covered. Test for salt and chili flavor. If not hot enough, add some chile powder. Just before serving, sprinkle the cilantro on top, if desired.
* To toast herbs and spices: use a small, heavy skillet. Place the herb or spice in the skillet over low heat. Shake the skillet until the aroma of the herb or spice is released. Be careful not to burn them. Then grind the spice if necessary.
** Look for chipotle chilies canned in adobo sauce. Puree the whole can and store in a jar in the refrigerator. They keep quite a while and are perfect for jazzing up all manner of foods. Use sparingly, though -- it's hot!