First of all, it is a liqueur that you rarely get and secondly, it tastes excellent:
You bring the dark stout to a boil and whisk sugar in it until it is dissolved [be careful, it can foam very much). Now add the sliced vanilla sticks, a small piece of fresh ginger and the very thinly peeled rind of an unsprayed lemon and let it all gently simmer together for about 15 minutes.
After cooling, blend with 1 quart of pure alcohol [95%}. Afterwards filter, fill into bottles and rest, also if it is hard.
To give away then just fill part of it in a nice bottle, maybe you can add or stick the recipe as a label.
Beautifully written this looks very good.