Bring water to boil in sm. saucepan with steamer basket.
Steam leeks until tender, approx. 5-6 min. Drain thoroughly.
Melt butter in med. saucepan over med-low heat. Add onion and cook until translucent, approx. 4 min. Stir in garlic.
Stir in cream, mustard, and salt and blend well.
Stir in wine. Heat to simmer.