Gâteau basque

Mix and chill the dough. Beat the 120 g softened butter with the 200 g sugar, then mix in the 100 g egg, 300 g flour, 11 g baking powder, 3 g salt and 30 ml rum until a cohesive dough forms. Cover and refrigerate for at least 60 minutes at 4 °C. The dough is smooth but not sticky and is firm after chilling at 4 °C. Cold butter-rich dough can be rolled and fitted without smearing. Keep chilled at 4 °C; the dough contains raw egg and flour.

Cook the pastry cream. Infuse the 500 ml milk with the split 5 g vanilla bean and bring it close to a boil. Whisk the 150 g egg with 125 g sugar and 40 g flour, temper with the hot milk, return to the saucepan and cook while whisking until the cream reaches 85 °C and bubbles gently for about 3 minutes; stir in the 30 ml rum. The cream reaches 85 °C, boils gently for about 3 minutes and becomes thick enough to hold whisk trails. Heating fully cooks the flour and egg mixture before it becomes the enclosed filling. Stir continuously and do not taste until fully cooked.

Cool the pastry cream rapidly. Spread the hot cream in a shallow metal tray, cover its surface and use an ice bath to pull down the heat quickly. Refrigerate and make sure it reaches 4 °C or below within 2 hours. The pastry cream reaches 4 °C or below within 2 hours and is cold and firm before assembly. Rapid shallow cooling limits time in the warm temperature range and keeps the dough from melting at assembly. Cover the surface and refrigerate at 4 °C or below as soon as rapid cooling has begun.

Line the 22 cm pan and enclose the cold cream. Roll the chilled dough to 4–5 mm. Use about 60% to line the base and sides of the 22 cm pan, spread in all the cold pastry cream, and close with the remaining 40% of dough, sealing the edge cleanly. The dough is rolled 4–5 mm thick, about 60% lines the base and sides, the cold cream forms an even layer, and the remaining 40% seals the top completely. Even dough thickness and a complete seal give the characteristic enclosing shell. Keep the cream cold during assembly and return the pan to the refrigerator if the dough softens.

Egg-wash, mark and bake. Brush the lid with the 25 g beaten egg, mark the traditional fork pattern without cutting through and bake at 160 °C for about 40 minutes. Probe discreetly and continue until the enclosed centre reaches about 93 °C. The surface is deep golden with a clear fork pattern, the centre reaches about 93 °C, and the cake feels set rather than fluid under the lid. The moderate bake cooks the enclosing dough while setting the custard again without burning the top. Use a clean probe through an inconspicuous point and avoid serving the custard-filled cake underbaked.

Cool completely before cutting. Cool on a rack for 90 minutes before slicing. Once fully cool, refrigerate rather than leaving the custard-filled cake out for extended holding. The cake is completely cool and the pastry-cream filling cuts cleanly instead of flowing. Cooling stabilises both the butter-rich crust and custard. Do not leave the custard-filled cake at room temperature for extended holding; refrigerate once cool.