Add oil, cumin seeds, garlic, ginger, shallot and leek to a medium pot. Cook stirring often, until fragrant.
Add curry paste, stir well and cook for a few minutes.
Add sweet potato cubes, stir and sauté on low for 10 minutes.
Add vegetable stock, tomato paste, salt and coconut milk and stir to combine.
Bring to a boil and turn down to a simmer for 10 minutes.
Remove some of the sweet potato and set aside. Blend the rest of the mixture in the pot with an immersion blender.
Add the sweet potato back to the mixture along with the beans and kale. Simmer for 10 minutes.
Check for seasoning before serving.