Over medium heat in Large stockpot, add butter and saute onions, celery and bacon bits until onions and celery are somewhat tender...start adding potatoes as they are peeled and sliced, stirring gently.
Midway through the peeling and slicing process, add milk and Half & Half, salt and pepper. Continue to add more potatoes as the milk starts to simmer. Be careful not to boil rapidly, just simmer. Add the bullion cubes and potato flakes. Stir occasionally and make sure soup is not getting so hot on bottom as it starts to stick to bottom of pan. Continue to cook for about 2 hours or until potatoes and celery are tender.
Garnish with shredded cheese, sliced green onion and more bacon bits. This recipe will make plenty for a crowd.