panade

Panade isn’t a soup you’ll see on restaurant menus: it’s made with stale bread boiled in milk, with butter and sometimes an egg. The word has been adopted in English for the technique of adding milk and bread (and sometimes egg) to meat, especially to meat loaf, to keep it moist and from shrinking when cooked.

Être dans la panade means pretty much the same as in English: ‘To be in the soup’.