Preheat and Prepare: Set your oven to 350°F (175°C). Follow the instructions on the cake mix box, but replace each cup of water with a cup of milk. Distribute the batter evenly between two 10-inch round cake pans greased with Baker’s Joy. Bake for 60-80 minutes, checking for doneness at the 60-minute mark and every 5 minutes thereafter. To test, insert a toothpick into the center of the cake; if it comes out clean, the cakes are ready.

Cool the Cakes: Let the cakes cool in their pans on wire racks for 30 minutes. Then, invert each pan onto a rack to release the cakes. Allow them to cool completely before assembling or storing.

Prepare the Butter: Leave 3 sticks of butter at room temperature for at least 30 minutes to soften.

Make the Frosting: In a stand mixer, combine two sticks of softened butter and one cup of shortening. Beat on medium speed until fluffy. Add 2 teaspoons of vanilla extract and mix well, scraping the sides of the bowl as needed. Gradually add 8 cups of powdered sugar, one cup at a time, mixing on low speed. Increase to medium speed and mix until the frosting is stiff and well combined.

Adjust Frosting Consistency: Add milk, one tablespoon at a time, beating after each addition until the frosting reaches a spreadable consistency. Avoid making it too runny.

Assemble the Cake: Trim the rounded tops of the cakes to level them. Cut one cake in half and stack the halves with frosting in between. Frost the top of the other cake and place the stacked halves on top to create a tiered effect. Frost the entire cake, adding more frosting if needed by repeating steps 4-6.

Add Pirouette Cookies: Arrange unbroken Pirouette cookies around the taller tier of the cake. Use broken pieces for the shorter tier, leaving a gap for the waterfall. Trim cookies as necessary.

Create the Waterfall: Using a piping bag with a #7 Wilton tip, pipe white frosting to outline the river, waterfall, and plunge pool. Pipe long, uneven lines to mimic flowing water, leaving the plunge pool area mostly untouched.

Paint with Blue Gel: Spread blue sparkle gel over the waterfall and river using a food-safe brush. Allow some white frosting to show through to resemble foam and light reflections. Apply more gel to the plunge pool, making it thicker in the center and thinner at the edges.

Add Foam Details: Use a #10 Wilton tip to pipe small amounts of white frosting at the base of the waterfall to mimic crashing waves.

Sprinkle Cookie Crumbs: Crush Biscoff cookies into fine crumbs and sprinkle them over any exposed frosting to create a “dirt” effect. Ensure the entire cake is covered with either cookies, gel, or crumbs.

Insert Trees and Dinosaurs: Place plastic trees into the cake, spacing them out for dinosaur figures. Use 8-12 trees, pressing larger ones deeper into the cake and covering gaps with cookie crumbs.

Pipe Grass: Mix green food coloring into the remaining frosting. Using a #233 Wilton tip, pipe grass around the trees and dirt areas, including the edges of the plunge pool.

Place Dinosaurs: Position dinosaur figures on the cake, pressing them slightly into the frosting to secure them. For a realistic touch, place one dinosaur’s foot in the plunge pool and add extra blue gel to create the illusion of water.