In a large bowl, cream together the butter, brown sugar and egg until well blended. Stir in the molasses. Combine the flour, baking soda, cinnamon and ginger; stir into the molasses mixture. Cover the dough and chill for at least 1 hour.
Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets. Roll the dough into walnut sized balls. Place the cookies 2 inches apart onto the prepared cookie sheet.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.