Heat the pot over medium heat. Add the oil and swirl to cover the surface. Add the scallions, kale and mushrooms. Sauté until softened, about 5 minutes.
Add the garlic, pepper and sage, and stir to mix the seasonings well.
Add the vegetable broth. Increase the heat to bring the contents to a boil. Add the lentils and oats. Stir vigorously. Reduce the heat to medium low to obtain a steady simmer.
Cover and continue to simmer for about 25 minutes until the lentils and oats are soft and the liquid is mostly absorbed. Stir occasionally to prevent sticking.
If desired, top with diced scallions, Parmesan cheese, toasted cashews or toasted pine nuts.