Warm olive oil in a large skillet over medium heat until it shimmers. Add finely chopped onion and cook, stirring often, until the onion becomes soft and translucent, releasing a sweet aroma, about 5 to 7 minutes. Ensure the onion does not brown by adjusting the heat as necessary.

Add minced garlic to the skillet over medium heat. Stir continuously for about one minute, ensuring the garlic becomes fragrant and turns a light golden color. Be vigilant to prevent any burning, as this can impart a bitter taste to the soup. Adjust the heat if necessary to maintain control.

Add the diced potatoes to the pot, stirring them into the mixture. Cook over medium heat for about 2 minutes, ensuring they are well-coated with the oil and aromatics. Stir occasionally to prevent sticking, and watch for a slight golden hue to develop on the edges.

Add the vegetable broth to the pot, stirring gently to combine with the potatoes. Increase the heat to medium-high and bring the mixture to a rolling boil. Once boiling, lower the heat to a gentle simmer, cover the pot, and cook for 15 minutes. Check that the potatoes are fork-tender before proceeding.

After draining the soaked cashews, add them to the pot over medium heat. Stir continuously for about 5 minutes, ensuring they are evenly mixed with the other ingredients. The cashews should become slightly golden and fragrant, indicating they are well incorporated. Avoid letting them stick to the bottom of the pot.

Carefully ladle portions of the soup into a blender, ensuring not to exceed halfway to prevent overflow. Blend each batch on medium speed until the mixture achieves a smooth, creamy consistency. Pause occasionally to check the texture. Once blended, pour the soup into a clean pot, ready for reheating or serving.

Pour the blended soup back into the pot over medium heat. Add a pinch of salt and freshly ground black pepper, stirring continuously. Allow the soup to gently simmer for 5 minutes, ensuring the flavors meld together. Taste the soup, adjusting the seasoning with additional salt or pepper if necessary, until it reaches your preferred balance.

Pour the freshly squeezed lemon juice into the simmering soup, stirring continuously for about two minutes. This step enhances the overall taste profile by adding a subtle acidity that complements the other ingredients. Ensure the lemon juice is evenly distributed throughout the soup, creating a well-rounded and cohesive flavor.

Place the soup back on the stove over low heat, stirring gently every few minutes to ensure even warming. Keep a close eye on the temperature, as boiling can alter the smooth consistency. Once steam begins to rise and the soup is heated through, remove it from the heat and serve immediately.

Ladle the hot soup into bowls, ensuring each serving is evenly distributed. Sprinkle chopped fresh parsley over the top, allowing the vibrant green to contrast with the soup's creamy texture. This garnish not only enhances the visual appeal but also introduces a subtle herbal aroma. Serve immediately to enjoy the soup at its best.