First, melt the butter. You can do this in a saucepan on the stove, but I find melting it in a batter jug in the microwave to be the easiest. Depending on your microwave power, this will take around 1 to 2 minutes.
While the butter is melting, place the wick into the paper cup and use the wick holder to hold the wick straight.
Once the butter is melted, add the salt and other herbs and seasonings and stir it well.
Carefully pour the melted butter into the paper cup, ensuring you don't disturb the wick.
Place the butter candle into the freezer for around one to two hours to firm up. The butter candle can stay in the freezer for as long as you need.
When the butter candle is set and you're ready to use it, take your loaf of sourdough bread. Using an identical paper cup to the one that you used as a mold for the butter candle, use a knife to cut a hole in the centre of the loaf of sourdough.
You only need to cut the top of the bread with the knife, then use your fingers to pull the bread out of the middle to form a hole for the butter candle to sit in.
Once you have a hole big enough, use your knife to cut the outside of the bread into pieces, without actually cutting the bottom of the bread. This will make the bread easy to tear off and dip into the melted butter.
When you're ready to serve, place the butter candle into the centre of the loaf of sourdough and light the candle wick. It will take around 15 to 30 minutes for the butter to start to melt after you light the wick.