Cream together butter, brown sugar, egg and vanilla.
In a another bowl, combing flour, baking powder and salt. Blend into creamed mixture.
Separate dough into two pieces: 1/3 and 2/3.
Chocolate Dough: In a small bowl, mix together cocoa powder and baking soda. Combine with 1/3 of the dough. Work 1 tablespoon water into the chocolate dough. Form into two 10" logs.
Take the other 2/3 of the dough and divide into two pieces. On a floured surface, roll each piece into a 10 x 4 rectangle. Place chocolate dough in center. Mold vanilla dough around chocolate dough, forming a log. Repeat with other piece of vanilla dough.
Wrap in plastic wrap and chill 2-24 hours.
Heat oven to 350°F.
Cut dough into 1/8" slices. Lay two slices side-by-side on a cookie sheet. These are the owl eyes. Next, pinch the upper/outer corners -- to resemble the horns or feather tufts that owls have at the top of their heads.
Next put a peanut butter chip in the center of each eye. Then add a cashew "nose" between the eyes.
Bake 8-10 minutes. Cool on a wire rack.