Fraisier

A modern classic of French pâtisserie. The génoise-and-mousseline strawberry gâteau has documented antecedents in Auguste Escoffier's late-19th-century strawberry cake (recorded in Le Guide Culinaire) and a kirsch-soaked sponge strawberry cake by Pierre Lacam around 1900, but the form most diners now recognise is widely credited to pastry chef Gaston Lenôtre, who in 1966 created a version of génoise soaked in kirsch syrup, mousseline cream and fresh strawberries finished with marzipan, naming it Bagatelle after the gardens of Bagatelle in the Bois de Boulogne west of Paris. The generic dessert has no single firmly-documented inventor; later chefs (Pierre Hermé, Christophe Felder and others) developed their own versions and the name fraisier became standard. The name comes from the French fraise, 'strawberry' (from Latin fraga), exactly paralleling the raspberry framboisier from framboise.

Cool and clean off the fork: the mousseline is firm but light, rich with butter yet not greasy, carrying vanilla and a faint almond note from the marzipan top. Against it the strawberries are fresh and juicy, slightly tart, and the kirsch-brushed sponge is soft and lightly boozy. A good slice stands upright with crisp edges, the strawberry wall holding its line. A poor one gives it away at the cut: weepy cream that slumps and beads, mealy out-of-season berries with no perfume, or a sponge so dry the syrup never soaked in.

The structural trick is the crème mousseline. It starts as a standard crème pâtissière (milk, sugar, egg yolks and a starch such as flour or cornflour, cooked until thick), but once cooled it is beaten with a large proportion of softened butter — commonly around one part butter to two parts pastry cream, and as much as one to one when a firm cake is wanted. Plain crème pâtissière, thickened only by gelatinised starch, stays soft and would slump under the strawberries. The butter changes that: chilled below its melting point the butterfat crystallises and solidifies, and because it is dispersed throughout the cream it sets the whole mass into a firm, sliceable solid that holds the vertical strawberry wall upright and gives a clean cut — the same fat that makes the cream soft and pipeable at room temperature is what stiffens it in the fridge. The génoise underneath is a fat-light sponge: whole eggs and sugar are whipped to a thick foam, then flour is folded in gently so the trapped air leavens the batter; with little or no butter in the crumb it stays dry and porous, which is exactly why it drinks up the kirsch syrup instead of turning soggy.