For the pastry, rub the flour, sugar, butter and salt together with your fingertips until the mixture resembles breadcrumbs.
Add the egg yolk and water and mix to form a dough. Turn onto a lightly floured surface, gently knead, wrap and chill for 30 minutes.
For the frangipane, beat the butter and sugar until pale and soft. Add the egg and almond essence, then fold in the flour and ground almonds. Set aside.
Roll the chilled pastry into a large circle and transfer to a lined baking tray.
Spread the frangipane over the pastry, leaving a 2-inch border around the edge.
Arrange the prepared plums on top.
Fold the pastry edges over the fruit, leaving the centre exposed.
Brush the pastry with egg wash and sprinkle with flaked almonds.
Bake at 180°C (160C fan) for 35–40 minutes, or until golden brown.
Remove from the oven and allow to rest slightly before serving.
To serve, mix the Crème fraiche, honey and vanilla and serve alongside.
