In a large pot over medium heat, sautée the onion, garlic and chilli in the oil for 2-3 minutes or until the onion is soft and translucent. Add the smoked paprika, thyme, coriander and cumin seeds and coriander stalks to the pot. Cook for 1 or 2 additional minutes.
Add all the veggies to the pot – kale, butternut squash, cauliflower and turnip(s) – cover with the tinned tomatoes and stock and cook, covered and over low-medium heat, for 30 to 40 minutes. Check every 15 minutes or so – the vegetables should be tender but not too soft and mushy. Have a taste and lightly season the stew with salt.
Take ½ cup of the stew broth and add it to a bowl. Add the tahini and whisk everything together until you get a creamy mixture. Add this mixture back to the pot and cook, uncovered and over medium heat, for additional5 minutes.