18 fluid ounces terflask
1 1/4 cups cold water
2 tablespoons unsalted butter
1 teaspoon salt
1/2 cup stout beer
In a standard saucepan over medium heat bring the water to a boil. Cool slightly.
In a small bowl mix together the pureed liquid, butter, salt and 1/2 cup of beer. With a wire whisk or electric mixer, turn the heat down to medium-low and blend until smooth.
Pour into glasses; top each glass with a small skewer of butter. Serve immediately after serving with the parmesan.