Since I have been asked and it seems I keep running into people who want to make yuja syrup I guess I should post. I just wish people would bequeath me some yuja, so I can make my own. *sigh* Oh well can’t get everything you want in life!
Yuja (Korean name), y`ou zi (One of the chinese dialects) or Yuzu (Japanese and much more familiar to the western world name) or sometimes generically named citron. The scientific name is Citrus ichangensis x Citrus reticulata var. austerajust in case you need it. Now I could be wrong on the scientific name, but I am thinking this is correct, but if someone can prove me wrong then please rectify the mistake! 
Thanks.
In Korea one of the ways yuja is used is to make it into a marmalade or syrup (with peels) to make hot and cold drinks.The marmalade/syrup has recently become very popular in Japan for tea and juice. Japan, Korea and China have many ways they use yuja; a lot of the sues being quite delicious.
Now, about the recipe. I don’t really have one. Okay don’t run away you will now know how to make the syrup like stuff soon enough, but I don’t have any access to fresh yuzu (actually not enough of them to make yuja cheong , and therefore have not really made a lot of this stuff. On top of that there are many ways to make it. I will give you several, but they are all basically the same. All of recipes rquire eating after they are made except for one that requires a month sitting, but soon after that it needs to be used.
Now for the recipes, they are pretty much what I hear or see poeple do with quantities. I son’t know who to attribute these recipes too, but all the generations of women that used the recipes. Now these are approximations of stuff I have been told, as no one really tells me exactly how their recipes go. Also if I have unknowingly infringed on someone’s copyright or I didn’t attribute you then let me know, but I don’t think I have, but I could be wrong.
Recipe 1
10 yuja
1 cup water
1 cup sugar or honey
Clean the yuja with hot water, and a little vinegar or salt to get rid of pesticides/dirt.
In a pot place the water and sugar on medium heat to dissolve the sugar. The sugar syrup should reduce 1/4 or so but do not let it boil or carmelize. It should still be clear with no pigment. Let it cool. (If using honey make sure all the honey dissolves and it may have a yellowish tint.)
Cut the yuja in half and then slice into half moon shapes (wedges) as thinly as you can.The thicker it is the longer it has to sit. Remember to discard the seeds. Place the yuja in a clean sterilized dry jar, and then add the sugar syrup (it can be warm but not hot!). Muddle the yuja with a clean spoon, and then keep out for a day or three in a dark cool place and then refrigerate. Some people will leave it outside the fridge for 1-2 months, but I have never tried. Anyone willing to send me some yuzu? *wink* *smile*
Recipe 2
Yuja however many you have, but weigh them.
80% by weight of sugar/honey to yuja. (if you have 10lb yuja you need 8lb sugar), or a 1:1 ratio is fine.
Separate the pulp from the peel. Slice the peel in half moon shape as thinly as possible.
Roughly chop the pulp discarding the seeds.
Method 1
In a clean cool, sterilized jar place some of the sugar (or honey) on the bottom, and then layer with the pulp, sugar/honey, peel, sugar/honey, pulp etc and alternate and ending with sugar, and then seal. Place in a cool dark place (frigerator will do) and let sit for 1-2 months. This is optional but some add a small amount of soju (about 1 kg fruit to 2 tablespoons), to take out the bitterness of the yuja. I personally like the sweet and bitter taste.
Method 2
Place the sugar and enough water to dissolve the sugar over heat, add the pulp and peel, and simmer for 10 minutes until it coats the spoon. Place in sterilized jars, and store in the frigerator. Eat soon.
Now you can make a marmalade out of the yuja, but none of the recipes I have seen used pectin. So I am assuming all the pectin comes from the yuja pith, or some recipes require you to boil some apple peels with the water to add more pectin to the yuja cheong recipe.
Super Easy small quantity version.
2 yuja
1 cup sugar
Small clean sterilized jar
Cut yuja in half then in moon shapes (wedges) layer yuja and sugar alternating in the clean glass jar. Alllow it to sit for 24 hours. Refrigerate. And use quickly or you can let it stand for a month then use.
Yuja Cha
Take your yuja cheong and place a spoonful (about a tablespoon or so) of the peel, and syrup in a cup. Pour a 1/2 cup of boiling water, and stir. Taste and adust to your preference. It is also drunk cold.
I hope you enjoy making yuja cheong.
If you have any questions please let me know! Btw. since I live in the Bay Area I usually just buy yuja cheong. I might not be able to do that the next place I move.
If you need some pictorials here are some places you might want to visit. Sorry they are in Korean, but if you can read Korean you have a lot more recipes at your finger tips. On the other hand you might want to see how google butchers the translations if you are bored.
I think the blogs name is beom nae but I am not that fluent in understanding what I read in Korean. But she/he has a lovely picture of making Yuja Cheong.
Here is a Image search on Naver.com for the yuja cheong if you are interested. Also sorry to say all of it is in Korean.