Heat the olive oil in a large pot or Dutch oven over medium heat.
Add the chopped onion and sauté for about 5 minutes until translucent. Add minced garlic and cook for an additional minute.
Stir in the sliced mushrooms and cook for about 8-10 minutes, until they have released their moisture and begin to brown.
Add the diced carrots, bell pepper, dried thyme, smoked paprika, salt, and black pepper. Cook for another 5 minutes, stirring occasionally.
Pour in the vegetable broth and add the diced tomatoes with their juice. Bring the mixture to a gentle boil.
Reduce the heat to low and let the stew simmer for about 20-25 minutes, allowing the flavors to meld.
If using, add the chopped kale in the last 5 minutes of cooking. Stir until wilted.
Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley.