Melt the dark chocolate in 30 second intervals, stirring in between each break.
Fill each cavity 1/3-1/2 of the way full with chocolate. Press the cookie into the cavity so that the chocolate comes up the sides. Repeat with all 6 cookies and then lightly tap to get air bubbles out.
Pour more chocolate over the cookie so that it’s completely covered and flushed with the top. Tap lightly again to get the air bubbles out. If needed, use an offset spatula to scrape the top and smooth it flat.
Refrigerate for at least 30 minutes.
Melt the milk chocolate (about 1/3 of the bag) the same way you did the dark.
Remove the cookies form the fridge and “release” them from the mold onto a cutting board. You can do this by pressing on the back of each mold so that the heat from your finger releases the cookie.
One by one, dip each cookie in the milk chocolate so that it’s covering the top 1/3 of the cookie. Let them set until the chocolate is firm.
Meanwhile, melt the white chocolate and put it into a piping bag with a small open tip or a bottle with a small tip. Pipe lines onto each cookie and let them set.