In a skillet, warm 1 teaspoon of olive oil on medium low heat. Add the garlic and white parts of the green onion, and cook for about 3 minutes, until fragrant.
Drain and rinse the soaked cashews, and then place them into the bowl of a high speed blender. Add the cooked onion and garlic, lemon juice, water and salt. Blend on high until smooth. Add more water as needed to thin.
Next bring a large pot of salted water to a boil over high heat. Add the penne pasta and cook as directed.
While the pasta cooks, in a medium sized bowl, add the sliced mushrooms and lightly drizzle with olive oil. Add the Cajun seasoning and stir until the mushrooms are evenly coated. Meanwhile add the mushrooms to the skillet used for the garlic and warm over low to medium heat. Cook for about 5 minutes, just until soft.
Once the pasta is done cooking, drain the excess water while reserving just a few tablespoons. Add the cashew cream to the pot with the pasta and stir until evenly coated, adding some of the reserved pasta water to thin if needed. Transfer the pasta to separate bowls, top with the mushrooms, remaining green onion, tomato, and fresh parsley. Serve warm and enjoy!
*Place cashews in a bowl and cover with water by a few inches. Soak for at least 6 hours or up to overnight. For a faster option, bring a pot of water to a boil, remove from heat and add the cashews. Soak for at least 30 minutes.**To make your own cajun seasoning, combine ¼ teaspoon salt, ¼ teaspoon pepper, ½ teaspoon garlic powder, ½ teaspoon onion powder, ½ teaspoon oregano, ½ teaspoon thyme, ½ teaspoon paprika (or smoked paprika) and a pinch of cayenne pepper (optional) in a small bowl and stir to mix.