Heat the olive oil in a cast-iron pot or Dutch oven.
Brown the paupiettes on all sides over high heat for a few minutes. Add the chopped onions and leek, cover with a lid, and cook for 10 to 15 minutes, turning the paupiettes and stirring the vegetables occasionally.
Pour in the white wine and let it simmer for 5 to 10 minutes.
Add the water and veal stock, then allow the sauce to simmer and thicken.
Serve hot with sautéed potatoes or homemade French fries.