What filling is commonly used in pastries like cream puffs and éclairs?

The filling commonly used in pastries like cream puffs and éclairs is custard. Custard is a smooth, creamy mixture made with eggs, milk, sugar, and often flavored with vanilla. In the context of cream puffs and éclairs, custard serves as a rich and luscious filling that complements the lightness of the pastry shells.

Cream puffs, which are made from choux pastry, are typically filled with a sweetened custard or crème pâtissière, which ensures they are both airy and indulgent. Similarly, éclairs, which consist of a long choux pastry filled with the same custard, provide a delightful contrast between the crisp exterior and the creamy filling.

While Bavarian cream is also a type of custard that is lightened with whipped cream and set with gelatin, it is not as commonly used in the classic preparation of cream puffs and éclairs. The other options—fruit preserves and chocolate mousse—are delicious in their own right but are not traditionally associated with these specific pastries. Therefore, custard is the quintessential filling that defines the experience of enjoying cream puffs and éclairs.