Heat a large pot over medium heat and add a tablespoon of oil. When shimmering, add chopped onion and cook, stirring occasionally, until translucent and fragrant, about 5 minutes.
Add minced garlic to the pot and cook for another minute until fragrant, being careful not to brown it.
Pour in the vegetable broth and bring to a gentle boil.
Add the broccoli florets to the boiling broth, then reduce heat and simmer for 10-12 minutes until the broccoli is tender and vibrant green.
Use an immersion blender to blend the soup directly in the pot, or transfer part of the soup to a blender and puree until smooth, leaving some chunks if desired for texture.
Stir in the nutritional yeast and plant-based cheese, then cook over low heat until the cheese melts completely and the soup becomes creamy, about 3-5 minutes.
Adjust seasoning with salt and pepper, then add a splash of lemon juice to brighten the flavors.
Let the soup sit off the heat for 5 minutes to thicken slightly and allow flavors to meld.
Serve hot, garnished with a sprinkle of black pepper or chopped herbs if desired, and enjoy the velvety, cheesy goodness.