In a small saucepan heat the saffron with the wine over moderately low heat until it dissolves. In a small skillet cook the leek in 2 tablespoons of the butter over moderately low heat, stirring, until it is softened, add the saffron mixture, and cook the mixture, stirring, for 1 minute. Let the leek mixture cool to room temperature. In a small bowl cream together the remaining 1 1/2 sticks butter, the leek mixture, the lemon juice, and salt and pepper to taste. Let the butter stand, covered, in a cool place for 1 hour to allow the flavors to develop. Serve the butter with seafood or vegetables.