Remove skin from each sole. With a sharp knife, make 4 fillets of each by cutting in 2 lengthwise near center bone, cut each half into 2 strips. Remove bones with tip of knife. Pound lightly to flatten & break the nerves. Rinse in cold water. Clean & chop bones, rinse, set aside.
To make fish stock, heat 1 tbs. butter in saucepan. Add onion, carrot, one-fourth cup shallots, & chopped fish bones, cook until vegetables begin to release juices.
Cover with water, add bouquet garni, cook on medium heat 20 min. skimming often. Strain stock through sieve lined with damp cheesecloth, return to pan.