Beat the butter with an electric whisk or in a small blender until pale and fluffy. Finely grind the timut pepper and cardamom seeds using a pestle and mortar, then stir into the whipped butter with a pinch of salt, if you like. Spoon into a dish or shape using a waxed wrap or baking parchment and chill until needed. Will keep for one week. Serve with crusty bread or melt onto grilled or barbecued chicken.