Cut the onions in half and clean them. Now chop them. Then add a drizzle of oil in a frying pan and caramelize the onions on a medium heat with the salt. Stir it every now and then to prevent the onions from burning.
Once the onions have a nice golden brown color deglaze the pan with the Madeira wine and also add the thyme, the vegetable broth and the garlic. Let this simmer on a low heat for at least 6 hours.
After that pass the broth through a fine sieve and use a small ladle to press out any liquid so you don’t waste anything!
Now when necessary reduce the broth till you’re happy with the flavor.
Then mix 0.5 a tablespoon of the potato starch with around 30 grams of water and while mixing add it to the boiling broth to thicken it. You’ll end up with a nice glaze.
Normally I always use Xanthan gum to thicken my broths, but for a hot broth you can always use potato starch as well. I wouldn’t recommend corn starch. This makes the clear broth cloudy.Â
