Place ghee in the basin of the instant pot then press the sauté button. Once the ghee begins to melt, add the carrots, celery, onion and garlic and sauté for about 5 minutes, until onion becomes translucent.
Press the keep warm/cancel button, add the cauliflower, chicken broth, hot sauce and a hefty pinch of both salt and pepper, then secure the lid, close off the pressure valve and press the Soup button. This will cook for 30 minutes once it comes up to pressure. Once the soup is done cooking, you can let it naturally release or do a quick release. Once you remove the lid, use an immersion blender to blend the soup until completely smooth. Taste to see if the soup needs any extra salt or pepper.
Turn the soup back onto the Saute function and add the rotisserie chicken and let cook down for 8-10 minutes, stirring every 2 minutes to keep from sticking. Press the keep warm/cancel button before serving.
Garnish soup with a swirl of ranch, hot sauce, green onions and cilantro.