Put the sugar in a pan and let it melt on a medium fire.

When all the sugar has melted, let it caramelise until it becomes a very dark amber colour.

Remove from the fire and add the butter and salt. Stir well.

Add the cream and stir (do not worry if the caramel hardens at this point, it will still melt during the next stage).

Put the pan back on the fire and cook until the caramel reaches 108°C – 226°F on a candy thermometer (I have done this even without a thermometer… keep in mind that it will boil at 100°C – 212°F, so keep boiling it for a few minutes (see pictures below).

Add the cream and milk to the caramel and cook on a low flame until the salted caramel has completely melted.

Let the mixture cool down and then chill very well in the fridge.

Add the alcohol and mix well. Filter it through a sieve and bottle it.

Keep it in the fridge for a couple of days and shake well before serving cold.