Green’s Dictionary of Slang

dish (out) v.

also dish up

[early 18C; mid-19C+] to give out, to apportion.

In phrases

dish out the gravy (v.) (also dish out the porridge) [puns + ironic use of gravy n. (2b)/ porridge n. (1)]

[1940s–50s] of a judge, to hand out a heavy sentence.