In a small sauce pan, melt butter over medium low heat. Add flour to the pan, and whisk together to make a roux (about 1 to 1.5 minutes) Add the chicken broth and milk, and whisk together to smooth out the lumps. Bring to a simmer and continue cooking until mixture thickens, about 2 to 3 minutes. Remove from heat and use as you would a regular can of condensed soup.