For the dough: In a saucepan, soften and brown the butter on medium heat. Let cool.
Combine flour, spices and sugar. Add the cold butter and the egg yolk and knead well by hand. Form a ball and cover with plastic wrap. Chill in the fridge for 30 minutes, until firm.
Roll out the dough (5-7 mm) and spread it out in a greased and floured pie pan. Place in the fridge for another 30 minutes. Prick with the tip of a fork and bake for 10-12 minutes on 400F
For the filling: cream the butter and sugar in an electric mixer. Puree two bananas and cut the other one into slices. Add banana puree and egg to the butter and sugar. Combine well before adding the ground hazelnuts. Spread out the slices of banana on the dough then pour banana-nuts cream on top. Top with chopped walnuts.
Bake in the oven for 25 minutes. Let cool before serving.