Basque Cake with Pastry Cream

Whisk together the flour, ground almonds, baking powder, and salt in a bowl and set aside. In a separate large bowl, beat the softened butter and caster sugar together until pale and fluffy, about 3 minutes. Beat in the 2 whole eggs one at a time, then the vanilla extract and rum, scraping down the sides after each addition. Fold in the flour-almond mixture until a soft dough just comes together — do not overwork it. Divide the dough into two portions, one slightly larger than the other, flatten each into a disc, wrap in cling film, and refrigerate for at least 2 hours, or overnight.

Heat the milk and double cream in a small saucepan over medium heat until steaming and just beginning to simmer at the edges — do not boil. Meanwhile whisk the egg yolks, caster sugar, and cornflour together in a bowl until thick and pale.

Slowly pour the hot milk mixture into the yolk mixture in a thin stream, whisking constantly to temper the eggs. Return the custard mixture to the saucepan over medium-low heat and cook, whisking constantly, until the custard thickens and large bubbles burst slowly at the surface, about 3–4 minutes.

Remove from the heat. Whisk in the vanilla extract, rum, and cold butter cubes one at a time until fully incorporated and glossy. Press a sheet of cling film directly onto the surface of the custard to prevent a skin forming, then refrigerate the crème pâtissière until completely cold and firm, at least 1 hour.

Preheat the oven to 180°C, or 160°C for a fan oven, or 350°F. Lightly butter a 20 cm round cake tin (at least 4 cm deep) and line the base with baking parchment.

On a lightly floured surface, roll the larger dough disc to a circle approximately 26 cm in diameter and about 4 mm thick. Carefully drape it into the prepared tin, pressing it gently into the base and up the sides so it overhangs the rim slightly.

Spoon the cold crème pâtissière into the pastry shell and smooth it into an even layer with the back of a spoon, leaving a 1 cm clear border around the edge.

Roll the second dough disc to a 22 cm circle about 4 mm thick and lay it over the filling. Press the edges of the top and bottom pastry together firmly to seal, then trim the overhang flush with the rim of the tin. Whisk together the egg yolk and milk for the egg wash, then brush an even layer over the top of the tart.

Use the tines of a fork or the back of a knife to score a traditional crosshatch pattern lightly across the surface — press only 1 mm deep so you do not cut through to the filling.

Bake on the middle rack for 45–50 minutes, until the top is a deep, even golden brown and the pastry feels set and firm when you press the centre very gently.

Allow the gâteau to cool in the tin for 20 minutes, then turn out onto a wire rack and leave to cool completely before slicing — cutting while warm will cause the crème pâtissière to run.