Spread butter in bottom of a 6-quart heavy pot. Add fish bones and heads, onions, parsley, juice and salt. Cook on Wolf cooktop over medium-high heat, covered, 5 minutes without stirring. Mixture will steam in its own juices. Add water and wine and bring to a boil. Reduce heat and simmer 25 minutes, uncovered, skimming off any foam. Pour stock immediately, cool broth uncovered. Cover and chill in Sub-Zero refrigerator. Stock will keep, covered in the refrigerator for 2 days or frozen for 1 month.