I am a huge fan of bitter liqueurs, at a trade show I picked up a bunch of big chunk bitter orange peel and decided to work on a recipe:
750ml 80 proof vodka or silver rum
2 tablespoons bitter orange peel
100ml sugar
50ml water
In an aging container, combine the vodka and the bitter orange peel. Let sit for 30 days, filter and pour back into the aging container. In a saucepan, combine sugar and water. Bring to a boil, stirring constantly. When sugar is dissolved, set aside to cool. When cool combine with the rum in the aging container stirring to combine. Let sit for a month, then bottle.
This bitter liqueur is very reminiscent of Campari or other amaro’s albeit less complex.