Chop the tough dark green ends off leeks and discard, keeping the white and light green stems only. Then chop leeks into roughly 1-inch pieces and wash thoroughly.* Add leeks to a large pot with coconut oil and bring to medium-high heat. Cook leeks, stirring often until soft and wilted (approx. 10 minutes).
Add chopped potatoes to pot and stir mixture until potatoes have softened slightly (approx. 10 minutes). Pour in water and simmer veg on low heat until potatoes and very soft and tender. (approx. 15 minutes).
While you are waiting for the potatoes to soften make your Cashew Cheese Sauce. In a blender add soaked cashews (strained), almond milk, garlic cloves, salt, nutritional yeast, dijon mustard, apple cider vinegar and cumin. Blend until smooth and creamy.** Pour cheese sauce into a bowl, or jug (as you will need the blender for the soup. No need to wash it out however).
Add leek and potato soup to blender and blend until smooth. Then pour back into saucepan along with cheese sauce. Taste and adjust flavours if desired (adding more salt, or cumin, or apple cider vinegar for brightness, or water to thin). Keep on a low simmer until ready to serve.
Add coconut oil to a small skillet with pumpkin seeds, rosemary and a pinch salt. Bring to medium-high heat and toast rosemary and pumpkin seeds until browned and perfumed, (approx. 3-5 minutes).
Divide leek and potato soup into bowls and top with fried rosemary and pumpkin seeds.