Heat the olive oil over medium heat in a large pot. Add the chopped onion and cook until soft. Then, add the minced garlic and red pepper flakes. Cook for another minute.
Put the broccoli florets in the pot. Pour in the broth. Season the soup with salt and pepper. Bring it to a boil, reduce the heat, and let it simmer until the broccoli is tender, about 15-20 minutes.
Once the broccoli is soft, use an immersion blender to blend the soup in the pot until it's smooth. Use a regular blender, but be careful with the hot liquid.
Taste and adjust the seasoning if needed. Serve hot, and you can garnish with grated cheese if you like.
Notes
Excellent soup; store in an airtight container. Refrigerate for up to 3 days or freeze for two months. Thaw in fridge or cold water; reheat on stove or microwave.Add Creaminess (Optional): If you want a creamier soup, stir in the heavy cream or coconut milk now.