Combine sugars. Mix the glucose syrup, sugar, and water in a small sauce pot. Cover with a lid, and bring to a light boil over medium-high heat. Try not to get the sugar stuck to the rim or walls of the pot.
Dissolve thoroughly. After a minute or so of cooking, lift the lid carefully, stir gently, and confirm that all of the sugar has completely dissolved. If any sugar remains, return the lid and boil for another 30 seconds. The goal is to allow the steam to wash any rogue granules of sugar down into the syrup. A single granule of undissolved sugar can make the whole batch crystallize like fondant, which you do not want. (Alternatively, you can use a wet pastry brush to wash down the sides of the pot. That’s the traditional method, but I find the steam method is more reliable and less messy.)
Add the fat and lecithin. Once all of the sugar is dissolved, set aside the lid and add the fat and lecithin. Stir to incorporate, making sure at all times that any utensil that touches the syrup does not have any undissolved sugar on it.
Cook to 118°C / 244°F. Stir gently every once in a while. If you prefer firmer chews, you can cook it two or three degrees higher. (If you live above 300m / 1000 ft elevation or the current conditions are very humid, see the note below.)
Add optional salt or acid. Once you’ve reached 118°C / 244°F, immediately remove from the heat. Add in any powdered salt or acid, and stir to incorporate.
Pour onto the baking mat. The hot syrup won’t spread as much as you might think, but give yourself plenty of room to work and make a mess.
Allow to cool partially, then add flavour and colour. This is a judgment call you’ll have to make yourself. You want the candy to cool as much as possible so that you don’t damage or flash off (evaporate) the delicate volatile compounds in your flavouring of choice. But, if you wait too long, the candy will start becoming too firm to effectively add the flavouring; this is especially true with liquid flavourings. My advice? Check the surface of the candy with your spatula until it starts to get difficult to spread, then quickly work in the flavouring and colouring. Between 60–80°C / 140–176°F is ideal. (Tips on flavouring here.)
Leave it alone. At this stage, the taffy will look like a gooey disaster and you’ll think you’ve botched it. You haven’t. Unlike hard candy, taffy needs to approach room temperature to be firm enough to handle. Go watch a few Youtube videos.
Pull! Once the taffy is cool, you can finally start to pull it. If you’re working on a silicon mat, you can fold it in half like an omelette a few times to get the process started before picking it up. If you’re working on a countertop or marble slab, you may need to sacrifice some of the sticky candy to the counter; if so move to a new, clean, lightly oiled section to work. Pull for 20-30 minutes until light, opaque, and satiny. (Detailed tips on pulling here.)
Cut and wrap. Using very lightly oiled scissors, divide the candy into more workable quarters or thirds then roll and stretch it into finger-thick ropes. Cut the rope into even pieces, then immediately wrap each piece in a square of parchment paper, twisting off both ends. Store them in an air-tight container to stop them from getting soft and sticky from humidity.