To make the pastry, sift the flour and baking powder above a big bowl, and stir to combine. Add sugar, 1 egg and the butter and mix until a slightly sticky but soft dough forms. You can also do this in a standing mixer.
Wrap the pastry in cling film and chill in the fridge for 30 minutes. Meanwhile, preheat the oven to 180°C and grease a 26cm springform tin with a little butter.
Once the pastry has cooled, roll out on a floured work surface to the thickness of 2-3 millimetres and slightly larger than the tin. Cover the bottom and the sides of the tin and save the excess pastry for the top of the pie.
For the filling, put the sugar in a thick-bottomed saucepan over low heat and melt until lightly golden, about ten minutes. Carefully add the honey and the cream and mix well. Add the chopped walnuts and hazelnuts and stir, coating the nuts evenly in the mixture.
Pour the nut mixture to the prepared tin and spread evenly over the bottom. Cover with the excess pastry in whatever pattern you like; I usually either opt for a make-shift lattice top, as pictured, or cover it entirely. Brush with the remaining egg until evenly coated.
Bake on the middle shelf of the oven for 30 to 35 minutes until the pastry is golden brown and the filling is bubbling and fragrant.