Beat the eggs with sugar to whitening and add the oil while stirring. Dissolve the hartshorn in 2-3 tablespoons of lukewarm water or milk and add it to the mixture, followed by lemon zest and lemon essence.
Add the flour gradually and mix with a mixer at first and then knead it by hand. You have to make a soft dough that can be rolled.
Allow to rest for half an hour, then roll out into a sheet with a thickness of 0.5″ (1.5 cm) and cut the cookies into the desired shapes. Arrange them on a tray with baking paper, decorate them with crushed or whole nuts and insert them to bake at 347°F (175 °C) in a preheated oven until pinkish.