Start with the very best duck breast you can get and trim the sinew off, give it a little massage to get rid of any blood still in the arteries, make sure it's well plucked and cut away any bits of flesh that are bloody. I usually detach the bits of loose skin which makes a nice duck jerky to snack on when slicing the main breast for friends.
Mix the salt and sugar together in a plastic food box, add the duck and massage the salt/sugar mix into the flesh and the skin, ensuring you get into all the nooks and crannies.
Pour in the molasses and make sure the breasts get a good covering of it, I often use a fork to spread it around.
Put the lid on the box and put it in the fridge for 3-5 days (longer if you prefer it more cured, less time if you like it a little more rare)
Turn the breasts over every day but leave the liquor in the box.
Once you're happy that the breasts have been cured enough for you, take them out of the fridge and wash all the cure off and out of the box, pat dry the breasts and wrap tightly in cheese cloth or an old tea towel and put back in the fridge uncovered to dry for upto a week.
At this stage the duck is ready to eat if you don't want to smoke it.
If you prefer it smoked (I think it makes all the difference) then give it a cold smoke over a fruit wood for 4 hours.
I built my own smokehouse which is a bit flamboyant but I smoke a lot of fish and meat.
If you don't have a smoke house then a cold smoke generator and a kettle BBQ is all you need - I have used a ProQ smoker for many years and still sometimes use it in the smoke house - See https://www.proqsmokers.com/cold-smokers
In my opinion Cherry Wood is the best for smoking duck but you could use Oak, Apple, Beech or whatever you have.
Once you've smoked the duck, put it back in the fridge - it will make the fridge a bit smokey but wrap it well in a tea towel again and then just take it out and slice as you like.
It's best to give it a few days if you can resist temptation before devouring, it should be OK for a month or more in the fridge but if I think I'm going to have it around for a while I tend to vac pac it and that also keeps the smokiness in.