Preparation Spread butter in bottom of a 6- to 8-quart heavy pot. Add fish bones and heads, onions, parsley stems, lemon juice, and salt and cook, covered, over moderately high heat, without stirring, 5 minutes. (Mixture will steam in its own juices.) Add water and wine and bring to a boil, then reduce heat and simmer, uncovered, skimming any foam, 25 minutes. Pour stock through a fine-mesh sieve into a bowl, pressing on and then discarding solids. If not using stock immediately, cool, uncovered, then chill, covered. Cooks' note:Stock keeps, covered and chilled, 2 days or frozen 1 month.
Preparation Spread butter in bottom of a 6- to 8-quart heavy pot. Add fish bones and heads, onions, parsley stems, lemon juice, and salt and cook, covered, over moderately high heat, without stirring, 5 minutes. (Mixture will steam in its own juices.) Add water and wine and bring to a boil, then reduce heat and simmer, uncovered, skimming any foam, 25 minutes. Pour stock through a fine-mesh sieve into a bowl, pressing on and then discarding solids. If not using stock immediately, cool, uncovered, then chill, covered. Cooks' note:Stock keeps, covered and chilled, 2 days or frozen 1 month.