Cheesy Potato Soup

This is one that Gina put in the cookbook. I use it all the time! It makes such a huge pot of soup. I use it all the time when I take a meal to someone, they can eat it and have plenty of leftovers and freeze some too. When I make it I usually freeze half of it.
5-6 potatoes (chopped)
2 small carrots (grated)
1 celery stock (chopped in small pieces)
1 onion (chopped)
3 cans chicken broth
1 cup flour
1 cup butter
1 box Velveeta (the 16oz size)
4-5 cans evap. milk

Cook vegetables in chicken broth until tender. In separate pan melt butter and slowly stir in flour. Add cans of milk and Velveeta and stir constantly until cheese is melted and sauce is thickened. Add cheese mixture to vegetables and broth.