Grate the rind from the oranges. Squeeze 1/4 cup fresh orange juice. Clean the carrots and trim the stems. If the carrots are small, cook whole; if they are larger, cut into any shape so they will cook in about 10 minutes. Peel the turnips and cut into 1/2 inch pieces. In a saucepan, cook the vegetables in the orange juice on slow heat until tender. Add the chicken stock and let the vegetables steep on a slow flame for another 10 to 15 minutes. Remove to a blender and puree until smooth; correct the seasonings. Make a compound butter by combining the orange rind, honey, mustard and herbs with softened butter. Halve the plums and then slice each half into thin slices that can be fanned out. Ladle the soup into bowls; garnish with a piece of the compound butter and the plums.
