Method

In a medium bowl, whisk together flour, cocoa, baking soda, baking powder, and
salt.
In
another bowl, beat butter and sugar until creamy, about 2 minutes with an electric
mixer.

Beat in egg, 4 ounces of melted chocolate, and vanilla. Gradually beat in flour
mixture
until blended. Divide dough in half. Shape each half into a roll 2" in
diameter.
Wrap rolls in
waxed paper and freeze for 4 hours or until very firm.
Preheat oven to 350F.

Line two
baking sheets with foil and coat them with cooking spray. Cut dough into 1/4"
slices.
Arrange 1" apart on prepared baking sheets.
Bake cookies 10 to 11 minutes.

Cool on sheets
for 1 minute then transfer to wire racks to cool completely. Repeat process
until all
cookies are baked.
To decorate the cookies, place the chopped milk chocolate
in one
small zip-lock baggie and the white chocolate in another. Microwave on high
1 minute or
until chocolate is melted. Knead until smooth. Snip off a tiny corner of each
bag and
drizzle chocolate over cookie. Let cookies stand until chocolate is firm, about
an hour.