Remove the stems from the mushrooms. Discard stems, then slice mushroom caps into strips and set aside.
Heat a generous glug of olive oil in a pot on medium heat. Add garlic, scallions, and sweet onion and cook for a couple minutes until fragrant and the onions are semi-translucent. Add the sliced mushrooms in and continue to cook for 5 minutes, stirring often until they shrink and have slightly browned.
Once the mushrooms have wilted, add in chicken broth, sake, miso, kosher salt, brown sugar, white rice and give it a mix to combine.
Bring the entire pot to a boil, then bring the heat down to low to reduce to a very gentle simmer. Cover with a lid and cook for 1 hour (stir frequently and scrape the bottom every 10 min so it doesn't burn on the bottom) until the water has reduced and the consistency resembles a creamy porridge.
After an hour, remove the lid and add heavy cream. Mix until combined, then ladle into bowls and add extra scallions and sesame seeds and enjoy warm!
