Hazelnut layer cake

Preheat the oven to 180 &degC.
Grease an 18 x 28 cm cake tin with butter or non-stick spray and line with baking paper.
Sift the flour into a mixing bowl and rub in the butter.
Add the sugar and mix.
Sprinkle 350 g of the mixture over the bottom of the cake tin.
Lightly whisk the crème fraîche and eggs together and add to the flour mixture in the tin.
Sprinkle with the nuts and bake in the centre of the oven for 45 to 60 minutes or until a testing skewer comes out clean.
Remove from the oven and cover with a sheet of baking paper.
Carefully turn the cake upside down and remove the bottom sheet of baking paper.
Return the cake to the oven, bottom facing up, and bake for another 10 to 15 minutes until the bottom is crisp.
Remove from the oven and turn the cake over again.
Leave to cool completely. Cut into squares and serve.