Especially during the holidays, you seem to always have left-overs. This is a wonderful way to use up any left-over mash potatoes you have laying around. It is a good and economical version of Panera Bread's Broccoli & Cheddar Soup.
In blender, puree chicken broth, thawed broccoli and shredded carrots. Transfer to 4-qt pot. Heat to boiling on medium-high. Wisk in mash potatoes and pepper. Simmer on low heat 10 minutes. Stir in cheddar cheese.