Preheat oven to 450 degrees. Place the cashews and 1 cup water in a high speed blender and process for a few minutes, until smooth and creamy. Add ½ teaspoon salt and process again. Set cashew cream aside. (Can substitute 1 cup whole milk instead of cashew "milk" if desired.)
Add potatoes to a large pot of salted water and bring water to a boil. Reduce to a rapid simmer; cook until potatoes are tender, about 15 minutes. Drain and return to pot. Using a potato masher, mash potatoes until mostly lump free; drizzle in the cashew cream a bit at a time, until desired consistency. Season with salt to taste.
Place the sliced leek rounds in a food processor and pulse several times to shred. Remove shredded leeks from food processor and set aside. Process the carrots and then the onions in the same manner, keeping all of the vegetables separate.
Heat the oil in a large skillet over medium heat. Add the shredded leeks, carrots, and onions. Sauté 5 to 6 minutes until vegetables soften a bit. Season vegetables with salt to taste and add the fresh thyme.
Add the ground lamb or beef and use a spatula to fully incorporate the meat in with the vegetables. Cook for about 5 minutes or until meat is no longer pink.
Use a fork to whisk in the flour. Season with more salt to taste. Stir in the Worcestershire sauce and tomato paste and cook for about 2 minutes, until all ingredients are fully incorporated.
Spread the meat mixture on the bottom of a 9-inch square casserole dish or on the bottom of individual ramekins. Spoon the potatoes over the meat and smooth with the back of a spoon. Brush the potatoes lightly with oil; bake for about 15 minutes or until potatoes are just lightly browned on top. Remove from oven and let sit 15 minutes before serving.
I like to leave the skins on my potatoes for added nutrition and fiber.To enhance nutrition and also make the cashews easier to blend, you can soak them in water for up to 2 hours and then rinse and drain before making the cashew cream. Leftover cashew cream can be stored in a mason jar in the refrigerator for three days.I always serve a BIG but simple salad on the side drizzled with good extra virgin olive oil and a bit of unrefined sea salt. Buttery soft mache lettuce is my son’s favorite.Potatoes are one food I always buy organic when possible. The potatoes in the Harrods photo were probably Yukon Gold, but I used Russet potatoes in my recipe because they were the only organic option. Either potato will be okay.Lisa recommends organic ingredients when feasible.