Finely chop the walnut halves. Beat the butter until soft. Separate the eggs. Beat the butter, egg yolks and sugar until fluffy. Beat the egg whites with a pinch of salt until very stiff. Fold the chopped walnut halves into the butter mixture. Fold in the egg whites. Mix the flour, cocoa powder, ground walnuts and cinnamon. Fold into the egg mixture.
Preheat the oven to 180°C (approximately 350°F). Line a baking sheet with parchment paper. Use a teaspoon to heap portions of the dough onto the baking sheet. Bake for about 15 minutes, until golden brown. Remove from the oven, cool on a wire rack and serve.