Heat a medium sized soup pot or brasier over medium heat. Once the pot is hot, pour in the oil.
Add the onions to the pot and stir. Saute the onions until translucent and quite soft, about 3 minutes. Add the carrots and celery to the pot and stir. Cook until the celery is softened and bright green, about 3 minutes. Season the vegetables with salt and pepper and stir.
Add the chili flakes, smoked paprika, thyme, and garlic to the pot and stir. Keep stirring until garlic is very fragrant, about 45 seconds. Add the tomato paste to the pot and stir. Break up the tomato paste with your spoon and stir to coat the vegetables.
Add the potatoes and navy beans to the pot and stir to coat in the seasonings. You should see a faint red slick at the bottom of the pot. Season the potatoes liberally with salt and pepper. Add the crushed tomatoes to the pot and stir to combine everything. Pour in the vegetable stock and stir once more.
Place the lid on the pot and bring the stew to a boil. Once boiling, lower the heat to a simmer and remove the lid. Simmer until the potatoes are quite tender, about 20 minutes.
Add the chopped green beans to the pot and stir. Simmer until green beans are tender, about 4 minutes. Add the kale to the pot and push it down into the stew with your spoon. Place the lid back on the pot so that the kale can steam a bit. Let the kale wilt for about 30 seconds.
Check the smoky and spicy white bean stew for seasoning and adjust if necessary. Serve the stew hot with ground black pepper on top, extra chili flakes, and chopped herbs of choice (I used chives from my garden).