An interesting point made by a chef i was watching on youtube
said that in one of his first jobs in a French restaurant,
he was assigned to the saucier
to learn how to make borderlaise sauce.
He was told that the size of the vegetables should be cut in
relation to how long they're going to cook for.

So he asked the saucier, "why have you cut these ones so small
if they have to cook for an hour and a half?"
The saucier looked at him, paused for a while,
then said "you're a genius"
From then on, the saucier changed his recipe from the
classical way of making it.

He said the flavour is so much better than when cut small
using the traditional classic French technique,
and was surprised that nobody had ever thought of it before.

The bigger the pieces of veg, the longer they take to release their
flavour.
If you cut them too small and say cook for 2 or 3 hours,(as in a base gravy) there's going to
be no flavour left.

Frank. 

it's easy to overlook this principle in the rush to get base on the go.

it even works in favour of speed too.

this crept up on a search to understand how heat destroys flavour. have subsequently only rough chopped veg for base.

given further prompt by DalPuri now going to adopt a cut in half strategy for onion, carrot etc

So onions in, say, quarters rather than slices? -which tbh at least fit in the pan easier!

For a base gravy,  no smaller than quartered I'd say.
(A whole roasted onion tastes completely different to roasted onion slices.)


p.s.  Cant stand whole roasted  onions! 

Thanks Dal! Got two on the go atm