Apple pie with sour cream batter and walnut streusel

Roll the shortcrust pastry 2 millimeters thick between two sheets of parchment and chill it in the refrigerator, not the freezer.

Line the mold with the pastry, trim with a knife and prick the base with a fork so it does not puff up.

Place on a baking tray and bake at 160 C for 10 minutes, taking it out before it is fully baked.

Roast the walnuts in the oven about six minutes at 160 C.

Sift the flour; work the cold butter, flour and sugar into a dry, homogenous mass, keeping the walnuts whole.

Press the streusel through a grid into equal-sized pieces and put it in the freezer.

Brush the bottom of the part-baked case with yolk and milk to seal the holes so the batter does not leak; let cool.

Mix the sour cream with the baking soda and let it stand a few minutes.

Whip the butter and sugar into a snow-white cream.

Add the warmed eggs to the softened butter in small portions, waiting for each to mix in.

Add the sour cream mixture and stir until smooth, then add the flour and mix evenly.

Core the apple with a Parisian spoon and cut into slices.

Fill the pastry case with the batter and lay in the apple slices; top with the streusel and walnuts.

Bake 40 minutes at 160 C; leave to cool before unmolding.