Heat olive oil in a large pot over medium heat. Once the oil is shimmering, add the onion. Saute until translucent.
Add in garlic and give it a nice stir. Add in celery and carrot. Saute for 5 minutes.
Add in lentils, stir well and then add in the sweet potato. Cook for 3-5 minutes.
Add in mushrooms, black beans and navy beans. Mix well with the ingredients in the pot. Add in crushed tomatoes.
Add salt, black pepper, smoked paprika, turmeric and cumin. Stir well to make sure all the ingredients are mixed with the spices.
Add vegetable stock or water. turn the heat to high and bring it to simmer. Turn the heat to medium high, cover and let cook for 15-20 minutes until all the ingredients are fully cooked. Add more water if needed.
5 minutes before serving, add Carolina style barbecue sauce.
Serve warm with sour cream.
Notes
For the slow cooker version, place all the ingredients except the barbecue sauce in the slow cooker and cook on high for 6 hours. Add the barbecue sauce right before serving.