Trim the tops and tips off the carrots and cut them into 1-inch pieces. Place these pieces in a medium-large saucepan with water. Cover and bring to boil. Lower the heat to medium low and simmer until the carrots are very tender, about 10-15 minutes. While the carrots simmer, heat the butter/ghee/oil in a small skillet. When the oil is hot, add the onion and sauté over medium heat for about 5 minutes. Add the garlic, ginger, salt and spices. Turn the heat way down low and continue to cook for another 8-10 minutes, until the onion are very soft and all of the ingredients are well mixed. Stir in the lemon juice. Pour the seasoned onions, carrots/water and toasted cashews into a blender in small batches, pureeing until a desired consistency is reached. Place in a pan and heat gently just before serving. A small pitcher of buttermilk may be passed around for individual drizzling.