I tried to do a coffee liqueur a few month back, for that I went the cold brew way (make a strong cold brew overnight, then add white rhum + sugar to reach the desired abv and sweetness). For that I used washed red bourbon coffee which has a stunning taste but that is a bit light (also it is a rather light roast).
I did a 22%abv and 20% sugar.
The result was great, the taste is very sharp and the bitterness is just right. But I felt that it lacked body and could be improved.
I recently discovered oil washes, so I tried to do another liqueur, this time by going through oil wash (mix ground coffee 2:1 with neutral oil, filter, sous vide the oil with rhum and then let settle in the freezer. Add water and sugar to reach desired abv and sweetness).
For that one I added 1/3 of the oil volume of cocoa butter and let sous vide for 2h30 before sweetening with demerara sugar to reach 25%abv and 15%sugar.
The result is the opposite of the first liqueur, bold, very good aftertaste, but lacks cleanness and sharpness of the first sip, the "hit" is missing.
That's when the idea struck:mix both!
The result is stunning, I have the best of both worlds.
If anyone want to reproduce :
Use botran white rhum
Light roast washed red bourbon (filter ground) for cold brew
Medium roast espresso ground for oil wash
Cocoa butter
Sugar/demerara sugar
A few drops of saline.