In a large saucepan over high heat, brown 1 pound of sausage (I used 3 links sweet Italian and 1 link hot Italian) in a little oil, potentially in two batches if the pan seems crowded. Remove the sausage to a plate.
Reduce the heat to medium and add the onion, carrot, and celery to the pan. Cook for 5 minutes, stirring, until the veggies have lost their crunch and the onion is translucent. Add 3 whole cloves garlic, then return the sausage to the pan. Add the lentils, wine, 2 ½ cups water, ¼ teaspoon salt, and the bay leaf.
Raise the heat to high again, and bring to a boil. Cover partially, reduce the heat to low, and simmer for 45 minutes to an hour, until the lentils are tender. You can easily make this ahead of time--cool before storing in the fridge and reheat in the pan for serving.
Just before serving, add 2.5 ounces fresh spinach and stir to let the leaves wilt. Taste for salt, adding more as needed. Remove the bay leaf.