Radish Top Soup

2 tablespoons butter
1 large onion, diced
4 med. red potatoes, diced
4 cups raw radish greens
4 cups chicken broth
1/4 cup milk
5 radishes, sliced 

Melt butter in a large saucepan over medium heat. Stir in onion, and saute until tender. Mix in potatoes and radish greens, coating them with butter.Pour in chicken broth.Bring the mixture to a boil. Reduce heat, and simmer 30 minutes.Allow the soup mixture to cool slightly, and transfer to a blender. Blend until smooth. Return the mixture to the saucepan. Mix in the milk. Cook and stir until well blended. Serve with radish slices.