Combine the shallots, white wine, and lemon juice in a non-reactive saucepan over high heat and reduce to 2 tablespoons.
Add the cream to the reduction. Once the liquid bubbles, reduce the heat to low. Add the butter, one cube at a time, whisking first on the heat and then off the heat. Continue whisking butter into the reduction until the mixture is fully emulsified and has reached a rich sauce consistency. Season with salt and white pepper. Store beurre blanc in a thermos until ready to serve.
Recipe courtesy of Alton Brown