French president François Hollande is portrayed as Queen Marie-Antoinette, who is supposed to have said "Let them eat cake" (the traditional translation of the French phrase "Qu'ils mangent de la brioche") upon learning that the peasants had no bread. In Peter Brookes' cartoon, the famous phrase becomes "Let them eat horse!" (a clear reference to the horsemeat scandal), and the 'peasants' protesting outside the palace are the other European leaders, who are demanding cuts. (There's a play on words here, since a cut of meat is a piece which is cut from a particular part of it, hence 'prime cuts', 'best cuts', 'choice cuts', etc.)
The cartoonist uses a historical analogy to highlight François Hollande's failed pleas for a relaxation of austerity and for more spending to spur growth. Just like Marie-Antoinette, he was out of touch with the popular mood, and left looking isolated.
The Findus 'beef' lasagnes which are at the centre of the latest episode in the horsemeat scandal were made by French company Comigel, adding another layer of irony to the cartoon.