This cheesecake has a chocolate brownie base topped with a creamy mint filling. The green tint adds an eerie touch, and when topped with a storm cloud of whipped cream with bats flying overtop, this cheesecake will send you into squeals of delight.
For the brownie base, preheat the oven to 350ºF (180ºC). Grease a 9-inch (23 cm) springform pan and line the bottom with parchment paper.
Pour the boiling water over the chocolate in a large mixing bowl, let this sit for a few seconds and then whisk until smooth (it will seem curdled at first, but it will smooth out. Whisk in the sugar, followed by the mayonnaise and then the egg and egg yolk. Whisk in the vanilla and peppermint extracts. Sift the flour, cocoa and salt overtop and whisk until smooth. Pour this into the prepared pan and bake for about 20 minutes, until the top surface of the brownie is matte. Let this cool completely before making the cheesecake layer.
Increase the oven temperature to 400ºF (200ºC). Using electric beaters or in a stand mixer fitted with the paddle attachment, beat the cream cheese on medium-high speed until fluffy, occasionally scraping the sides of the bowl. While still beating, gradually pour in 1 cup (200 g) of the sugar, stopping at least once to scrape down the bowl. Beat in 1/2 cup (125 mL) of the sour cream, the cornstarch and the extracts, again scraping the bowl as you go. Lightly whisk the eggs and yolk in a cup and add this to the cream cheese gradually, this time mixing on low speed. Use a toothpick to add a little leaf green colour and mix in. Pour this over the cooled brownie base and bake for 10 minutes at 400ºF (200ºC) then lower the oven to 225ºF (107ºC) and bake for another 40 minutes. Turn off the oven and open the oven door, leaving the cheesecake to sit an additional 15 minutes before removing to a rack to cool.
As soon as the cheesecake is out of the oven, run a palette knife around the inside edge of the pan to loosen the cheesecake. Whisk the remaining 1/2 cup (125 mL) of sour cream and remaining 2 Tbsp (25 g) of sugar along with Kelly green food colour paste, and spread this over the top of the hot cheesecake. Once the cheesecake has cooled completely (test by touching the bottom of the pan, not the sides) chill overnight.
To decorate the cheesecake, remove the cheesecake from the pan and coat the sides of the cake with chocolate cookie crumbs before placing it onto a platter. Tint the whipping cream with just enough black colouring to make it a stormy grey colour. Whip the cream until it reaches a soft peak and whip in the sugar and skim milk powder (this stabilizes the whipped cream). Dollop and spread this over the cheesecake, but not fully covering the green top.
Roll out the black fondant (use icing sugar sparingly, as you roll) to about 1/4-inch thick and cut out 5-6 bat shapes. Insert the floral wire or skewers into the bottom of each bat and place on a plate or tray to dry, about 5 hours. Use the quick royal “glue” in a parchment piping cone to glue on the eyes and then insert the skewers into the cake, so the bats look like they are flying over the clouds. Chill the cake until ready to serve.
The cheesecake can be baked and chilled a full day ahead of serving, and decorated up to 6 hours ahead.
*To make quick royal icing “glue”, simply whisk about 1/2 cup (65 g) of icing sugar with a little water until thick without dripping. Spoon this into a parchment cone and use as needed. Allow 1-2 hours to dry.