In a mixing bowl, mix butter, sugar and brown sugar using beater so that they mix well together.
After that put eggs one by one and beat to make a smooth paste.
Now add rest of the dry ingredients including, flour, baking soda and cream of tartar and mix to form a smooth dough.
Roll the dough length wise and then wrap the dough in a plastic sheet and put in fridge for 30 minutes.
When the dough become stiff and set cut into thin slices and place them on cookie sheet to bake in oven for 8-10 minutes at 350 F
Serve the delicious cookies with tea after cooling them at room temperature.