Melt the butter in a small saucepan over medium-low heat. Add garlic and shallots; cook and stir until transparent, about 3 minutes. Season with tarragon, salt and white pepper. Increase the heat to medium, and stir in the white wine and lemon juice. Bring to a simmer, then whisk for 1 minute. Remove from the heat and sprinkle in parsley. Pour over your favorite white fish before serving.
