1. Sift together flour, cocoa powder and bicarbonate of soda into a bowl. Make a well in the center of the flour mixture, add sugar, almonds and eggs and mix well to form a soft dough.
2. Turn dough onto a lightly floured surface and knead until smooth. Divide dough into 4 equal portions. Roll out each portion of dough to make a strip that is 5 mm / 1/4 in thick and 4 cm / 1 1/2 in wide.
3. Place strips on a baking tray lined with nonstick baking paper. Brush with egg yolk and bake at 180°C/350°F/Gas 4 for 30 minutes or until lightly browned. Cut strips into 1 cm / 1/2 in slices, return to baking tray and bake for 10 minutes longer or until dry.