Welcome to the forum newbrewby! I guess I have a question to lead off with. From your description above it sounds like you're going to mix store bought Black Rock cider with dextrose and apple essence. Is that correct? Also, do you plan to carbonate? I ask because this can impact what method you choose. Of course you have different options depending on if you plan to keg or bottle and what other equipment you have available to you. Without more info from your setup I'm just going to take a few shots in the dark. Personally, I think the easiest way to make a sweet cider is to allow it to ferment to dryness, stabilize it with kmeta and sorbate, then sweeten to taste. This is the preferred method by many other folks in this forum as well. You could also skip the stabilizers and do stove top pasteurization as mentioned in the sticky in this forum. Remember if you go the cold crash route you will always need to keep your cider cold. If you don't fermentation will start back up, which can cause bottle bombs or an over pressured keg. Also, there is no guarantee that cold crashing will stop fermentation. Most of the time it works. But there are plenty of folks who've experienced otherwise.