In a large bowl combine butter and peanut butter; beat until creamy. Add brown and white sugar and beat until fluffy. Beat in egg, vanilla extract and baking soda until well blended. With mixer on low, mix in flour just until blended. Cover and chill for 1 hour, or until firm.
Preheat oven to 350 degrees F (175 degrees C).
Shape 1 level tablespoon of dough into 1 inch balls. Taper each ball at one end into a teardrop shape. Press flat on one side. Place flat sides down, 2 inches apart on ungreased cookie sheets. Press the sides of the dough in to raise the 'backs' of the mice, as dough will spread slightly during baking.
Gently push 2 peanut halves in each 'mouse' for ears, and 2 pieces of green candy for eyes. With a toothpick make a hole 1/2 inch deep in the tail ends.
Bake in preheated oven for 8 to 10 minutes, or until firm.
Transfer to a cooling rack and insert licorice pieces as tails.
