Melt butter in a 4qt saucepan on medium-low. Whisk in the flour to make roux. Now add the milk and the broth. Add corn. Cook and stir over medium heat until mixture comes to a boil and thickens slightly. Boil 1 minute more. Stir in the crab and shredded cheese. Cook and stir over low heat until cheese is melted. Serve.