Melt white chocolate in a microwaveable bowl for 30-second intervals. Stir after each interval until melted.
Stir in peanut butter until mixed well. Add broken cookie pieces and stir until distributed throughout the white chocolate mixture.
Cover a cookie sheet with parchment paper and pour the chocolate mixture on it, spreading it to form an even layer.
Place the semisweet chocolate chips in a microwaveable container and heat for 30-second intervals until melted. Stir after each interval. When the chocolate is melted, spoon it into a plastic zipper bag. Cut the tip off of one bottom corner.
Now, draw spider webs on the slab of white chocolate by drawing spirals. To make a web, start at the middle of the web and create a small circle. Keep circling, getting larger with each rotation. When the "web" is as large as you want, end it by overlapping the chocolate on what you have drawn.
Insert a knife (or toothpick) into the middle of the first spiral and pull it through the dark chocolate to the outside of the circle. Some of the chocolate will drag with the knife, which makes it look like a spiderweb. Continue to pull it from the middle to the outside, spacing each pull about 1 1/2 to 2 inches apart (for the large webs).
Place 1 or 2 pairs of candy eyeballs on each web to represent a little spider looking around.
Repeat the web instructions, making large and small webs all over the layer of white chocolate. Then, place the bark into the refrigerator to chill and set.
With a sharp knife, score around the webs. Scoring will make it easy to break the bark, keeping the "webs" intact.