Ratatouille
From Tardis Wiki, the free Doctor Who reference
Ratatouille was a simple dish made from tomatoes, onion, garlic, chilli powder, courgettes and fresh herbs.
Helen Sinclair selected ratatouille as an easy meal for the Eighth Doctor to cook. The Doctor later assured her, however, that it would have been awful. (AUDIO: Wild Animals)
Nardole mockingly called Ratatoskr ratatouille. (PROSE: I Am the Doctor)
Behind the scenes
It was not established whether Nardole was referring to the dish or the 2007 Disney and Pixar movie.