Chef Paul Berglund cleverly mixes melted butter with softened butter, so the finished spread has a creamy texture and mild, nutty flavor. Slideshow: How to Make Cultured Butter
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.
Gradually whisk the remaining 4 tablespoons of butter into the browned butter. Refrigerate until slightly thickened, 15 minutes. Season with salt and serve.
The burnt butter can be wrapped in plastic and refrigerated for up to 3 days. Bring to room temperature before serving.