In a deep full steam table pan (or divide evenly among 2 standard full steam table pans), combine potatoes, Ultimate White Cheese Sauce, milk, onions, 10 ounces Mild Cheddar Cheese, pimento, and garlic powder.
Cover. Heat on full steam, about 45 minutes, until potatoes are tender.
Using an immersion blender, purée soup until mostly smooth, leaving a few pieces of diced potatoes may be left in the finished soup.
Add broccoli and hot pepper sauce.
Cover. Continue cooking, about 15 minutes, until soup reaches 165°F for at least 15 seconds.
CCP: Heat to 165°F for at least 15 seconds
Top soup with cheddar cheese and green onion, if desired.