The encyclopaedia of gravy
Mushrooms are rich in glutamate, and drying them generates large amounts of guanylate — the combination that makes mushroom gravy taste convincingly meaty.
Two mechanisms, stacked¶
Glutamate. Mushrooms are among the most glutamate-rich foods in the vegetable kingdom. That gives them a savoury taste straight away.
Guanylate. When mushrooms are dried, enzymes break down RNA in the cells, generating substantial quantities of guanylate — a nucleotide that on its own tastes of very little, but which amplifies glutamate umami several-fold.
A dried mushroom therefore carries both halves of the umami synergy in one ingredient, which is why 10 g of dried porcini does more for a gravy than 200 g of fresh mushrooms. See umami in gravy.
Shiitake in particular¶
Dried shiitake are exceptionally high in guanylate, and are the basis of the savoury depth in a great deal of East Asian vegetarian cooking. In a British-style mushroom gravy a single dried shiitake alongside porcini adds noticeable weight.
Browning adds a third layer¶
Fresh mushrooms are about 90% water. Cooked gently they poach in their own liquid and stay pale and rubbery. Cooked hard in a wide pan, the water evaporates, the surface temperature rises past 140 °C, and the Maillard reaction produces roasted flavours on top of the umami already present.
This is why every mushroom gravy recipe insists on high heat, a wide pan and patience:
- Mushrooms release water — the pan looks wet and nothing browns.
- The water evaporates — the pan sizzles.
- Only now does browning begin. This is the stage most cooks stop before.
Salt timing¶
Salt draws water out of mushrooms by osmosis, which delays browning. Salt them at the end of cooking, not the start.
In practice¶
For the best meat-free gravy:
- Brown fresh mushrooms hard, for the Maillard flavours.
- Add dried mushrooms and their soaking liquid, for the guanylate.
- Add a glutamate source — soy, miso or yeast extract — for the synergy.
See mushroom gravy and vegan gravy.
Mushroom dislike¶
Some people have slightly immature palates which mean they claim they do not like mushrooms. I didn't as a child, but by the age of 14 onwards, I couldn't get enough of them. Take from that what you will.