Place the egg in a plate along with soda and salt, pour sugar into a glass, and cut off a piece of butter and place it in a plate. Pour flour into a deep container.
Mix eggs with sugar, add a pinch of salt. Using a mixer, beat until smooth, then add the melted butter. Add baking soda slaked with vinegar. Stir and add flour in portions, continuing to stir the dough. The dough should be like thick pancakes. Heat the pan over a fire and spoon out the dough. Cookies are baked for 2-3 minutes on each side over moderate heat.
Place the cookies on a flat plate and garnish with berries.