Originally Answered: Ile-de-France cuisine?
Sadly you have picked a topic on which there is very litlle to write. The people who live in Ile-de-France eat the same dishes as everywhere else in France or which are local specialities that originated elsewhere and there is no special gastronomic dish which is just specific to the region. Eating customs are exactly the same as in the rest of France, and, in any case, these days observance of certain customs are fast disappearing and foods that were eaten at a specific time of the year such as fish on Fridays or during Lent, pancakes on Shrove Tuesday, or turkey at Christmas, are now eaten all year round. You have to bear in mind that dishes that have made a name for themselves such as Coq au vin or mushroom omelet are eaten everywhere in France.
However there are some produce which are specific to the region such as Champignons de Paris which are grown in caves,and old quarries, the Faro apple and the Grolay pears that are grown in local orchards as the Montmorency cherry which is used for preserves and jams. The Houdan poultry is locally popular for its unusual dark flesh and particular taste, and it is suited to slow cooked recipes. Other locally made specialities are Moutarde de Meaux, Brie and Coulommiers Cheese. Crayfish and river fish from rivers and canals. Two local liquors/ digestives are Grand Marnier, exclusivement made at Neauphle-le-Château, et le Noyau de Poissy and the local cider is called Cidre briar. Two locally made small pastries are Niflettes ( made for All Saints day in the region of Colommiers) and Roseaux du Grand Morin. Rose petal jam is a also a speciality of the region.
Dishes which are popular or originate from the region are:
Les bouchées à la reine, le navarin d’agneau, le potage st-Germain, la tête de veau sauce gribiche, la gibelotte de lapin, la soupe gratinée aux oignons.
Paris–Brest, Saint Honoré, galette des rois Parisienne, choux Chantilly, chouquettes, brioche Nanterre, brioche parisienne, tarte Bourdaloue, Moka, puits d'amour, Opéra, millefeuille, savarin et flan parisien.