For my brother Christian’s 16th birthday, he requested a mint slice cake. That was weeks ago and I’ve been thinking about how to execute it ever since. I was tickled pink by his request as I have loved Arnott’s mint slice biscuits since the dawn of time and as a consequence of my deep abiding love for them I no longer permit myself to keep them in the house – ours is a deeply dysfunctional romance.
In the planning stages for this cake, I thought about just making Steph’s (of raspberri cupcakes fame) gorgeous Mint Slice Cake but for me, the best thing about a mint slice is the textural differences – the crunch of the biscuit, the smooth mint fondant and the glossy firm chocolate coating. Steph’s cake looked amazing, but I realized I didn’t want to just make a cake that looked like a biscuit – I wanted to try to replicate the texture of a Mint Slice, just on a larger scale.
For the base, I didn’t think a biscuit recipe would give me the proportional thickness or crunch that I wanted, and I knew a standard chocolate cake would be too fluffy. At first I planned to have a brownie base, but I decided against this as I didn’t want it to be too fudgy. Eventually I settled on a sort of macaron/meringue torte hybrid, as I reasoned it would have the crispness i was looking for but would also be substantial enough to support the fondant layer & ganache, particularly when sliced and served. I made the batter using a bastardized macaron method, but substituted hazelnut for almond meal as I felt it was more chocolate-y (perhaps a subliminal callback to my beloved Nutella?) and added some chopped chocolate to the batter as well. At the last minute I also threw in some coffee powder to make the chocolate really sing.
For the mint fondant layer, I used this simple peppermint cream recipe – just egg white, sugar and peppermint essence, with the quantities tweaked just a bit to get the proper soft texture. I initially had looked at a lot of buttercream recipes but was wary of the fact that buttercream often has a yellow/cream tint to it. I really wanted the peppermint filling to look exactly like the real thing, as white and clean as possible. Using raw egg whites isn’t for everyone, but I reasoned that there would be no pregnant, young, elderly or otherwise immunologically weakened people eating the cake, so I went with it! It turned out beautifully, with the same soft texture as you find in a real mint slice, and no oiliness.
The chocolate coating was the simplest thing to decide – I simply used a chocolate ganache, with a ratio of 2:1 chocolate to cream to encourage it to firm up when poured. I did at one point consider using tempered chocolate to get a perfect glossy crunchy finish, but I don’t own a candy thermometer and besides, there’s a limit to even my culinary perfectionism/insanity!
Recipe with detailed instructions after the jump…