Arrange wings in shallow baking pan.
Heat butter, soy sauce, sugar, water mustard and garlic powder if using, until butter and sugar melt.
Cool; pour over wings and marinate at least 2 hours, turning once or twice.
Bake in same pan at 375F for 1-¼ to 1-½ hours, turning occasionally. (Use the plumpest chicken wings you can find; if your market only has the normal scrawny ones, don't cook longer than 75 minutes)
Drain on paper towels and serve.
