Place the leeks and wine in a saucepan over high heat and bring to a boil; lower the heat and cook at a simmer until the liquid is reduced to approximately 1/3 c. Remove the pan from the heat and stir in the butter, a few pieces at a time. Add the cream, and return the pot to the very low heat, whisking to prevent scorching, and cook 1 minute. Season with salt and pepper and remove from heat.