Dave Plowman (News) wrote:

Usually called a serving hatch.

Quite!

Normal way would be to face the opening with wood - about 1" thick - to
the exact thickness of the walls. The bottom piece might well be larger to
act as a sort of shelf large enough to take plates safely. Make good with
one coat plaster up to the wood, then fit architraving of your choice to
form a frame.

Then wait a few years and brick it back up again ...