A reliable stock for when fish bones and shrimp shells are in short supply.
Heat in a medium heavy skillet over medium-low heat:
Add and cook, stirring, until the onion is soft:
Add:
Stir for about 1 minute, then stir in:
Simmer, partially covered, for 20 minutes, skimming and stirring occasionally. Strain and use immediately or let it cool, cover, and refrigerate for up to 4 days.