Make the Coffee Chiffon Cake

1. Line only the bottom of a 11-inch baking sheet pan (do not grease the sides) and preheat the oven to 160°C (320°F)
2. Microwave the milk for 30 seconds and then dissolve the instant coffee in it. Let it cool.
3. In a mixing bowl, beat egg yolks with sugar until pale and thick. Add oil and vanilla extract, mixing until emulsified. Stir in the cooled coffee-infused milk.
4. Sift in cake flour, baking powder, and salt. Mix until just combined.
5. Beat egg whites with lemon juice until foamy. Gradually add sugar and whip until stiff peaks form.
6. Add a small portion of meringue to the yolk batter to loosen it. Then gently fold in the rest in stages until fully incorporated.
7. Transfer the batter into the pan, leveling it with an offset spatula. Tap the pan on the counter to release air bubbles.
8. Bake in a preheated oven at 160°C (320°F) for 10–12 minutes.
9. Let the cake cool in the pan before unmolding.

Make the Coffee Whipped Cream

1. Add the double cream, vanilla extract, and instant coffee to a saucepan.
2. Heat the double cream gently and dissolve the coffee. Let it cool completely, then chill for at least an hour.
3. Sift in icing sugar and add a pinch of salt. Whip at medium speed until stiff peaks form — not too stiff or too soft. Refrigerate until ready to use.

Make the Crunchy Toffee Topping

1. Add sugar, butter, and water to a saucepan and bring to a boil. Stir constantly until butter melts.
2. Once the butter has melted, stop stirring but keep an eye on the colour. When it turns amber, remove from heat.
3. Pour onto a silicone mat and let it harden completely.
4. Break into small pieces.

Assemble the Cake

1. Slice the cooled chiffon cake into three even slices, around 8.5 cm (w) each. 
2. Spread a layer of coffee whipped cream between each layer.
3. Add the toffee crunch into the middle of the layer and cover with a thin layer of coffee whipped cream.  
4. Repeat steps 2 & 3 for the second layer.  
5. Place the last slice on top and cover it with a thin layer of coffee whipped cream. 
6. Chill the cake for 15 minutes to set. 
7. Pipe a border around the top of the cake and sprinkle the crunchy toffee pieces on top for texture and extra flavour.
8. Slice and serve this delicious coffee chiffon cake! The combination of airy cake, creamy coffee whipped cream, and crunchy toffee is simply irresistible.