White sugar - I have always used granulated white sugar for this recipe, with half a cup in the cake and another half in the sauce.  Cocoa Powder - I prefer Dutch-processed cocoa powder, which I previously purchased from Takealot. I am confident it would also be effective with other varieties.
Oil - Any mild oil, such as canola, sunflower, or olive, or a combination of these, will work well. 
Boiling Water - This is added to the cake to enhance the chocolate flavor of the cocoa and into the sauce to dissolve the coffee. 
Eggs - From large to jumbo sizes, all are suitable. In the recipe, three eggs are separated; the yolks are incorporated into the cake batter, and the whites are whisked and folded in as the final ingredient. The inclusion of baking powder and whisked egg whites causes this recipe to rise significantly, resulting in a delightfully light cake. Ensure that you use a sufficiently large baking vessel.
Salt - It may be a pinch, but I believe it enhances the cake.
Baking powder - Baking powder is typically gluten-free, though it often contains cornstarch.
Vanilla Essence - I've noticed the discussion about alternatives such as vanilla paste and extract, but the cost is prohibitive, and I only have essence available.
Instant Coffee Powder -I usually enjoy Jacobs or Douwe Egberts coffee, but they are pricey, so I make do with what's available.
Caramel (plain or cappuccino) - The recipe is designed for a larger version and indicates using half a tin; however, you may choose to use the entire tin if you prefer. Whisking is crucial as it softens the caramel, making it easier to spread.
Cream - Fresh, Orley Whip, or UHT Whipping cream are all suitable choices for this recipe, with caramel being the only other dairy component. I prefer it with an additional dollop of cream on top.
Peppermint Crisp - A Peppermint Crisp is my preferred choice for crumbling on top, but I've also used Peppermint Aero and even Cadbury's Bubbly Mint flavor in the past.