Preheat the oven to 180°.

In a medium saucepan, melt the butter and sugar together. Stir in the cocoa powder, then the crushed cornflakes. Gradually stir in the flour.

Transfer the mixture into a non-stick square baking tin (clean and reuse the saucepan to make the fondant).

Bake in the preheated oven for 20-25 minutes or until it starts to brown around the edges. Once baked, set aside to cool down fully.

For the fondant centre: Place the flour and sugar in a medium heavy based saucepan. Whisk in the milk and cream. Increase the heat to just below boiling, then keep stirring for at least 6 to 8 minutes over a fairly high heat until the sauce has thickened to a custard-like consistency (use a wooden spoon to scrape around the inside edges of the saucepan where the mixture might catch, removing the pan regularly from the heat source as you do so).

The next step is to cool down the mixture rapidly (otherwise the filling may split when you incorporate the butter). To do this, transfer the sauce to a clean mixing bowl and whisk vigorously to reduce the temperature and cool fully.

Once the mixture is completely cooled down, whisk in the cubed butter until the mixture is smooth and light.

Use the tip of a cocktail stick dipped in food colouring to mix colour through. Add in peppermint essence (or extract), adjusting the amount to suit your taste. Spread the fondant evenly over the base and refrigerate for 30 minutes or until the fondant is firm.

For the chocolate top: Melt the chocolate in a bain marie (a bowl set over a saucepan of simmering water) until there is a smooth consistency. Pour the chocolate over the firm mint filling using a spatula to spread it into an even layer. Refrigerate until the chocolate layer hardens. Before cutting, remove from the fridge, wait 10 minutes and cut as desired into neat bars, squares or triangles with a very sharp knife. Store in a sealed container in the refrigerator.

Variation
Vary the bottom layer with either a chocolate brownie or chocolate cookie base.