Prepare cake batter according to package instructions. Add mint flavoring. Stir to combine. Bake at 350°F in a greased, parchment paper lined 9-inch round spring form pan for 35-40 minutes or until a toothpick inserted in the middle comes out clean. Let cool completely. Cut cake horizontally, so that you have 2 layers. (You might need to level the top of the cake as well if it has a dome shape.)
You will be using the spring form pan again, so wash and dry it. Line with plastic wrap, making sure you have some overhang on each side. Place a 9-inch round cake board in bottom of pan. Then take two pieces of parchment paper that are 15" x 5" each and place around the inside edge of pan.
Place one cake half in the bottom of the lined cake pan. Spread half of the ice cream over cake. Repeat with remaining cake and ice cream. Freeze for at least 4 hours or overnight.
Garnish with chocolate syrup, sprinkles and (thawed) frozen whipped topping.
Serve immediately. Store in freezer for up to 5 days.
Note: If you want to pipe the whipped topping, scoop it into a plastic pastry bag fitted with a 1M pastry tip and pipe onto cake. You should have it ready before you take the cake out of the freezer.