Sift together the flour, baking powder, baking soda and salt. Set aside. Beat together the butter and sugar until light and fluffy. Beat in the eggs, one at a time. Add 1/2 cup of the ground pistachios together with the flour mixture to the butter and sugar. Lastly, add the buttermilk and beat until well combined.

Divide the batter evenly between the two cake pans. Bake for 30 to 35 minutes, until tops spring back when lightly touched. Transfer pans to a wire rack to cool for 10 minutes. Turn cakes out onto rack to cool completely.

Filling: In a food processor, pulse ricotta and cream until smooth. Add salt, vanilla, cinnamon and icing sugar and process to combine. Transfer to a mixing bowl and stir in the 3/4 cup of chopped chocolate. Chill in the refrigerator for at least 1 hour.

Use a serrated knife to trim the tops of the cakes to level, split each cake into 2 layers. Brush the edges of the cakes with the melted chocolate and pat some of the reserved pistachios onto the chocolate. Refrigerate a single later until set (5 to 10 minutes).

Place one cake layer on a cake stand and spread with filling evenly over, then place another layer on top. Repeat with the remaining cake layers and filling, finishing with a cake layer, bottom side up. Refrigerate at least one hour. Sprinkle with powdered icing sugar and pistachios and spread extra filling on top if desired.