Mix together pudding and milk and whisk for 2 minutes. Refrigerate for 5 minutes until firm. 

Finely crush 15 chocolate sandwich cookies with a food processor and set aside. Coarsely crush, or break apart the remaining 15 chocolate cookies. Set aside. 

Place vanilla cookies into a food processor and process until fine crumbs. Place into a resealable sandwich bag. Add 1/2 teaspoon water and lots of green food coloring. Seal the bag and knead until the cookies are green. 

To make mushrooms, place peanut butter chocolate covered cookies onto a flat surface, face down. Place mini chocolate chips into a resealable bag but do not seal. Microwave on 50% power for 30 seconds and knead the chocolate. Repeat until the chocolate is completely melted, about 2 minutes total. Cut a small tip into the corner of the bag and pipe onto the center of the cookie. Carefully place a wafer onto the chocolate and hold until set. Repeat until you have the desired number of mushrooms. Let stand for chocolate to harden completely. 

Once chocolate is hard and stems are attached, use red frosting to cover the tops. Sprinkle with crushed white candy melts. Let stand, ideally in a bowl, or a cup filled with sugar, until ready to assemble. 

Slice round cake in half, creating 2 rounds. Place one round into the trifle dish and top with half of the pudding, half of the whipped topping and the crushed chocolate cookies. Repeat layers, ending with a layer of finely crushed chocolate cookies. 

To assemble the top, place some "piles or mounds" of finely crushed cookies in places. Push mushrooms into the trifle, add candy rocks, and candy flowers as well as green moss to decorate and complete the top. 

Serve immediately or refrigerate, loosely covered until ready to serve.