Preheat oven to 350F. Butter an 8" springform pan. Set aside
In a large heatproof bowl over simmering water add chocolate, butter and sugar, melt and whisk until mixture is smooth and glossy. Set aside to cool down.
In smaller bowl beat the yolks until they break up. Pour into cooled chocolate mixture. Stir in all the ground hazelnuts.
Beat egg whites and salt into a soft peak then fold into the chocolate mixture ⅓ at a time until incorporated.
Place batter into your prepared pan and bake 35 minutes or until center is firm and springs back.
cool and then dust with good quality cocoa.
Recipe by Proud Italian Cook at https://www.prouditaliancook.com/2013/02/flourless-chocolate-and-hazelnut-cake.html