En deux coups de cuillère à pot

Literally: In two strokes of the pot ladle

Example: “Ma grand-mère prépare une pâte à crêpes en deux coups de cuillère à pot.” — My grandmother whips up crêpe batter in two shakes of a lamb's tail.

English equivalent: In two shakes of a lamb's tail

Origin: It appears just before the First World War. A cuillère à pot is a large ladle, big enough to empty a pot or serve a heaping portion in a couple of strokes, and that speed is the whole point — the phrase most likely comes from military or prison kitchens, where rations were served fast. A second account derives it instead from a naval boarding saber whose spoon-shaped guard protected the hand, and which settled an argument in one or two blows; Alain Rey passes over that in silence and Claude Duneton rejects it outright. A third is delightful and definitely false: Antoine de Bourbon, king of Navarre, is supposed to have announced the birth of the future Henri IV to his court in a sentence punning on cuillère à pot — en deux coups de cul hier à Pau, two strokes of the backside yesterday at Pau.