Peel the mango and cut into small pieces. Place in a small saucepan, then add the white wine, mustard seeds, and lemon juice. Bring the mixture to a boil.
Reduce the heat to medium, and simmer softly for 5 minutes. Puree the mixture, pass through a fine strainer, and let cool. Mix the mustard into the mango mixture. Season to taste with vinegar, salt, and pepper.