In heavy-bottomed stockpot large enough to hold entire recipe, melt butter over medium flame.
Add onions and saute until translucent, about 5 minutes. Add the flour and stir to make a roux. Cook for 5 minutes over low flame, stirring constantly. Be careful not to allow the roux to brown.
Slowly incorporate the water while stirring with a whisk to avoid lumps. Add wine, clam base, parsley, dill, and bay leaves. Simmer for 30 to 45 minutes over low heat. Whisk in desired amount of half-and-half. Add the scallops and slowly poach just until they begin to turn opaque and firm, about 3 minutes. Be careful not to overcook scallops.
Recipe courtesy of The Mooring Restaurant