With most sauces and nearly all types of gravy you will need to use a thickening agent at some stage. This may be one of any number of things. The most commonly used are starches of some kind, because they all have the quality of swelling up in any liquid to which they are introduced. But it’s important to note that they also tend to behave differently.
Arrowroot, for example, has an interesting property. It tends to clarify any liquid into which it is introduced.
This is great for fruit sauces but may not be quite so effective with a meat-based gravy. It gives it an artificial appearance in my view, although you may quite like it and if you do, use it.
Starch compounds such as arrowroot, corn starch and potato flour need to be mixed with a cold liquid before being added to anything hot. They should be added a little at a time and allowed to cook for a while after each batch.
This needs to be done at the end of the preparation, because the thickening effect doesn’t always last that well. Kept on the heat, liquids thickened by starch tended to thin out again after a time.
Using flour
Don't worry that flour will make your gravy lumpy! Providing there is a fat present, flour will behave itself, and even if it doesn’t it will still whisk into the gravy or sauce.
The best way to use it is either as a roux, or as a beurre manié. These are basically the same thing but used in a slightly different way.
Both are a mixture of half flour and half butter (or other fat if you prefer) and both produce the same result – they thicken liquids.
To make a roux
Put an ounce of butter in a small saucepan and bring it to cooking heat, then add an ounce of plain flour and cook it while stirring. The length of cooking time will depend entirely on the color you wish to achieve.
The flour will darken with prolonged cooking, giving you a browner sauce as a result.
Once your mix is the color you wanted to be, take the pan off the heat and add half a pint of stock while whisking vigorously.
Please forget everything you have ever read about this process. The stock does not have to be cold, or hot, or added a little at a time. Just slosh it all in and whisk away. Then return the pan to the heat and bring it to the boil.
The resulting gravy will need to be cooked for at least a further two minutes, otherwise it will tend to have a raw finish, thanks to some uncooked starch. Just leave it on a low heat, but cover it to prevent a skin forming.
Even if one does form, you can usually whisk it back in and if not, strain it before serving.
Beurre Manié
Named for the chef who invented it, no one really knows how or why this works, but it does and it’s very effective if you need to thicken a large quantity of liquid, or one that already has food cooking in it.
Using the same measurements as for the roux, the trick is to slightly soften the butter and mix it with the flour. You then drop little nuggets of this mixture into the liquid to be thickened and bring it to the boil while stirring.
As the flour cooks, so it will blend into the liquid and thicken it.
Sweet sauces
Much depends on the base of your sauce in the first place and whether you intend it to be hot or cold. Fruit juices, for example, can be reduced while adding liquid glucose. This will produce a shiny sauce that is very stable when cold.
By stable, I mean that it won't separate and it won't move around the plate much, which is advantageous if you are trying to produce a particular effect.
Hot sauces are usually thickened with cornstarch or arrowroot. The latter will be clear while cornstarch produces a generally cloudy effect. Both need to be added with caution. Overdoing it can produce a sauce which is practically inedible.
The golden rule is to add a little at a time, and if the mixture becomes too thick add some more liquid.
Egg yolks, gelatin and even cream can all be used as thickening agents. Eggs, for example, are used as the base for all types of custard, including things like lemon meringue pie.
Once again you need to experiment and see what suits you. A sauce which is very runny when hot, may nevertheless become thick and clingy as it cools down.
Toffee sauce is a good example of this. It’s simply a reduction of sugar and water into which cream is stirred just as it starts to go brown. Left to cool it will look like, behave like, and taste a lot better than bottled caramel topping.
Vanilla sauce is somewhat similar. I make mine from three egg yolks whisked with 2 ounces of vanilla-infused sugar, onto which I pour 250 milliliters of hot cream. This is then cooked to the required consistency but without boiling.
For special events I use a vanilla pod instead of the flavored sugar. A classic example of egg yolks being used as a thickening agent.
Be inventive
As time goes by and you become more experienced, you will find yourself developing your own techniques.
Try to think outside the box. For example, why not thicken a sauce for lamb with red currant jelly? Or even a mixture of mint sauce and gelatin,
Remember, whatever you are trying to do only you know whether or not you have achieved it. So the consistency of the sauce you serve is exactly how it should be as far as your guests are concerned. Don’t make yourself feel a failure by apologizing for it.
If it looks good, tastes good and complements the food it is served with you have done your job brilliantly. Who cares if it’s a bit thin, or you can cut it with a knife? There will be people who like it either way and both ways.
The secret is not to let on. Cook it with flair – serve it with panache
