Heat the oil in a large pot over medium heat until shimmering and fragrant.
Add the chopped onion and sauté for about 5 minutes, stirring often, until it turns translucent and releases a sweet aroma.
Stir in the minced garlic and cook for another 30 seconds until it becomes fragrant and slightly golden.
Add the broccoli florets to the pot and cook, stirring occasionally, for about 5 minutes until they turn bright green and start to soften.
Pour in the vegetable broth and bring the mixture to a gentle simmer. Cover and cook for 10 minutes, until the broccoli is tender but not mushy.
Meanwhile, drain the soaked cashews and transfer them to a blender along with a cup of the cooked broccoli and some of the broth. Blend until silky smooth, about 1-2 minutes.
Return the blended creamy mixture to the pot and stir in the nutritional yeast. Season with salt and pepper to taste.
Warm the soup over low heat for about 5 minutes, stirring gently, until heated through and flavors meld. Add lemon juice just before serving for brightness.
Taste and adjust seasoning if needed. The soup should be velvety, vibrant green, and fragrant with a cheesy aroma from the nutritional yeast.
Serve hot, garnished with additional nutritional yeast or fresh herbs if desired. Enjoy this comforting, dairy-free bowl of goodness!