You may be doing it exactly according to recipe, but your sauce will still be thinner than it should be. Fortunately, there are a few tricks to thicken your sauce.
By leaving the sauce on the stove for longer, the water will slowly evaporate, so your sauce will probably thicken on its own.
Do not add cornstarch directly to your sauce, as the sauce may form lumps. Take a little of your sauce and mix it with the cornflour until you have a smooth mix, then mix that through the sauce.
It is also better not to add flour directly to the sauce. Mix flour with the same amount of butter (for example 20 grams of flour and 20 grams of butter) and add the mixture to your sauce.
Roux is a good base for many homemade sauces. Read more tips for cooking without packages and bags .
Crème frache can slightly alter the taste of your sauce and make your sauce creamier. Only choose this option if you don't mind.
Split an egg. Add a spoonful of sauce to egg yolk and mix it. Then you can add the mixture to your sauce to make it a bit thicker.
The starch will thicken your sauce. A little mashed potatoes will thicken your sauce. Yes, powder from a bag to make mashed potatoes also works.
Because you have extra ingredients you may need some extra seasoning.
