Step 1

In a medium skillet, cook 4 tablespoons of the butter over moderately high heat, swirling the pan, until the milk solids are very dark brown, 3 to 5 minutes. Pour the brown butter into a bowl, leaving the dark solids behind; let cool to room temperature.

Step 2

Gradually whisk the remaining 4 tablespoons of butter into the browned butter. Refrigerate until slightly thickened, 15 minutes. Season with salt and serve.