Rinse the lentils under cold water and set aside.
In a large pot or Dutch oven, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes, until translucent.
Add the minced garlic, diced carrots, and diced celery. Cook for an additional 5 minutes, stirring occasionally.
Stir in the sliced mushrooms and cook for 5-7 minutes, until the mushrooms are golden and their moisture has evaporated.
Add the dried thyme, smoked paprika, and cumin to the pot, stirring well to combine for about 1 minute.
Pour in the vegetable broth and add the rinsed lentils, diced tomatoes with juice, and the bay leaf. Bring the mixture to a boil.
Once boiling, reduce the heat to low and cover the pot. Simmer for 25 minutes, or until the lentils are tender, stirring occasionally.
Stir in the chopped kale and cook for an additional 5 minutes until the kale is wilted.
Remove the bay leaf and season the stew with salt and pepper to taste.
Serve warm, garnished with fresh parsley if desired.