Cut the root ends off of the leeks then cut them in half lengthwise. Thinly slice them and add to a large bowl of cold water and rinse well. Allow them to sit for a few minutes for the dirt particles to fall to the bottom of the bowl. Scoop the leeks out using your hands and transfer to a clean bowl.
Meanwhile preheat a heavy bottom stock pot over medium flame. Sauté the leeks in a light drizzle of olive oil ( use a splash of water, veggie stock or white wine for WFPB & Plantricious diets) and a pinch of sea salt until wilted and they start to caramelize at the edges. You might need to add more liquid so keep a close eye on them.
Optional: reserve about 1/3 of the caramelized leeks for garnish or to add back into the soup if a chunky texture is desired. In my opinion this really takes the soup over the top.
Add the carrots, bay, thyme and cashews and give everything a good stir. Add the potatoes then pour in the vegetable stock.
Bring the soup to a simmer and cook about 20 minutes until the potatoes and carrots have softened. Stir in the nutritional yeast and turmeric at this point if using it. (If a chunky texture is preferred, reserve some of the cooked potatoes and gently mash them before adding back into the soup).
Carefully transfer the soup to a powerful blender and puree until smooth and creamy on the hot liquid setting. Work in batches if needed and be mindful of the escaping steam.
Adjust seasonings to taste with sea salt and black pepper then serve garnished with the reserved caramelized leeks, scallions, chives or fresh dill.
Optional: Finish with a drizzle of cashew cream if desired.
Slow Cooker Method:
Add all the soup ingredients except the herbs for garnish to a slow cooker and cook on low for 6-7 hours. Transfer to a blender and puree until smooth. Garnish with the reserved herbs and a drizzle of cashew cream.
Instant Pot Method:
Press the saute button on the Instant Pot and when the display reads hot add a splash of veggie stock and the leeks. Stir and cook until wilted and start to caramelize at the edges.
Add the carrots, potatoes, cashews, bay and thyme. Stir in the veggie stock. Put the lid on the pot and set the “ steam release “ knob to the “ sealing “ position.
Press the “ Pressure Cook or Manual “ button and the “ + - “ button to choose 8 minutes. Let the pot naturally release the pressure for 15 minutes then manually release the remaining steam.
When the pin in the lid drops you can open it and discard the bay leaf and thyme sprigs. Carefully transfer the soup to a blender together with the nutritional yeast if using and puree until smooth. Season to taste with sea salt and serve garnished with the fresh herbs.
If you would like to give your soup a brighter golden color make sure to only use the white and pale green parts of the leeks and add 1/2 teaspoon of turmeric into the soup.