Heat olive oil in a large soup pot over medium heat.
Add diced onion and cook until softened.
Stir in minced garlic and sauté briefly.
Add chopped carrots and parsnips to the pot.
Stir in cubed sweet potato.
Cook the vegetables for 3–4 minutes to lightly soften them and develop deeper natural flavor before adding broth.
Pour vegetable broth into the pot.
Sprinkle in ground cumin if using.
Season lightly with salt and pepper.
Bring the soup just to a gentle boil, then reduce heat promptly to maintain a soft simmer.
Reduce heat and simmer for about 20 minutes until vegetables are tender.
Stir in chopped kale, cook 3 more minutes, then serve warm.