the.com/steamed
Anger cooked low and slow, escaping in visible little puffs of rage.
means Either food cooked over boiling water's vapor, or a person quietly furious and about to lose it.
from From Old English 'steam,' the rising vapor of hot water — the angry sense borrows the kettle's about-to-whistle pressure as a metaphor for barely contained fury.
Gentle methodSteaming preserves more nutrients than boiling.
Slang splitMeans angry in US, drunk in old British slang.
Pressure logicBoth meanings hinge on heat building toward release.