In a large saucepan or soup pot, heat coconut oil over medium low heat. Add onion, celery and garlic and cook and stir until onion softens and is translucent, about 10-12 minutes. Stir in red lentils.
Add squash cubes and broth, cumin, salt and pepper. Simmer about 15 minutes and add shiitakes. Simmer about 10 minutes more, stirring occasionally, or until squash cubes and shiitakes are both tender.
Taste for seasoning and serve.