I promised my food groupies a dissertation on gravy and I keep my promises.
There is this myth that making gravy is difficult. No, it isn't difficult, BUT it's intensive and trying to do it at the same time as all the other things you are doing when serving a meal is a bit of a bother. Even with assistance, I find this to be one of the frustrating aspects of cooking. For that reason I am trying to get into the habit of saving the meat juices from one roast dinner, and using them for the next one.
Anyway, there is more than one way to make gravy, but you need the same ingredients no matter what.
Some meat juices.
If you have these you don't even need the roast meat/pan. You can make gravy out of the blue as it were. You can even make gravy using other types of fat (butter, olive oil) but we are concerned here with using the fat from the same thing as we are pouring it over.
What most people do is take the roast meat out of the pan, and put the pan up on top of the stove, skim off most of the fat from the juices, add flour, whisk like crazy, then add stock, and flavourings.
This is a classic gravy method, but it does assume that you have the facility to do this. I don't. My roasting pan is huge, if I want to put it on top of the stove I have to remove ALL of the others pans in use, which as noted earlier, only works if I'm not actually cooking a whole meal and trying to serve it RIGHT NOW.
So, what I do is pour off all the fat and juices into a jug. separate out the fat and juices and do the thing in a saucepan.
The next question is about stock. I've posted about this before but I want to stress something right here and now. If you find it difficult to make stock, or you just don't have time, good quality stock cubes will do just fine. I use them unashemedly, and here's my rationale.
Stock made from stock cubes is not as good as good home made stock, but it's infinitely better than bad home-made stock.
Gravy made from meat juices and good stock cubes is EXPONENTIALLY better than commercial gravy.
There is only one commercial gravy I will even eat, and that's Knorr Gravy Granules. I use this for things like sausages, because nobody, not even Gordon Ramsey, can make gravy out of the juices from sausages. It cannot be done. Yes, I know there is such an entity as "sausage gravy", but 1) it's not actually gravy, and 2) it's not what I'm seeking.
Even then, I use vegetable water to make it up, rather than plain water, as it tastes sterile otherwise.
So, here is a step by step guide to making a good gravy in a saucepan.
1. Pour off all the meat juices that you have into a large jug. Scrape the pan well. If you have a turkey you probably won't need to scrape.
2. Let the fat rise to the top, and skim it off into a separate container. This is the fiddliest part of the job. You can buy special jugs with the spout at the bottom, but I can't get on with them. Use a flat spoon and skim.
3. Now put a few spoonfuls of the fat into a saucepan over a low heat. Fat is flavour but too much fat is greasy, so you don't need very much.
4. Stir in enough flour to make a paste. This lump is called a roux. Scientifically it should be half fat and half flour, but it's just as easy to eyeball it as to weigh it. And it is MUCH easier to judge by eye how much flour you need faced with just the fat, than when adding it to a mixture. Start with just a little, and add more until you get your paste. If you can pick the paste up with your fingers - but only just - it's right. It shouldn't be as dense as pastry, but it shouldn't have any "drip" to it either.
5. Cook this gently for about a minute, moving it around.
6. Now add back the meat juices very slowly while whisking, a little at a time, so you don't get lumps. If you have a large turkey this may be sufficient liquid to get your gravy to the thickness required. If not, now add stock, again slowly, whisking constantly, thinning the gravy out to the desired texture.
7. Now taste it. You may be happy with just salt and pepper added (if you used a commercial stock cube you may not need extra salt, so check first), or you may want more flavour. We like ours with herbs added, and you can also add wine, garlic, onions (cook onions first, either separately, or in the fat right at the beginning) etc.
If you follow those steps it should work fine. The usual issues people have are with lumps (from not whisking enough), runny gravy (adding the liquid too fast and overdoing it), or tasteless gravy (using poor quality stock).
If you want to plan ahead, you can save the meat juices by letting them go completely cold in the fridge (will become a jelly-like texture). At this point it is even easier to skim off the fat, as it settles and thickens from chilling. You can then freeze them separately. Then, next time you have a matching roast dinner, you can prepare the gravy leisurely while it cooks.
You can also freeze gravy. It will separate when thawed but is easily whisked back together over a low heat. It WILL be a little thinner, so make any gravy you intend to freeze a little thicker initially.