Preheat the oven to 160C Fan/180C/350F/gas mark 4 and grease and line the base and sides of a 23 cm / 9 inch loose bottomed or springform tin.

If you have an induction hob, add the chocolate and butter to a pan and place over a medium heat, stirring little and often until melted and smooth. If you have a gas hob, place the chocolate and butter to a glass bowl and sit on top of a pan filled with simmering water. Stirring well to melt.

Once melted, remove from the heat and add the cocoa powder and salt. Use a balloon whisk to mix until smooth. Leave to one side to cool.

Into a stand mixer bowl, add the egg whites and cream of tartar to a stand mixer bowl. Using the whisk attachment, mix on a medium speed until the whites are stiff but not dry. Begin to add the caster sugar to the bowl 1 tbsp at a time, allowing each addition time to combine before adding the next.

Once all the sugar has been added, continue mixing until the meringue has reached stiff peaks – be careful to not over whisk to prevent the protein from breaking down. You will know if this has happened if the texture begins to look crumbly and begins to separate.

When your chocolate is at room temperature, add the egg yolks. Whisk well until smooth – this will begin to thicken but shouldn’t seize. If it does, add the pan back to the heat and warm gently.

Add the flours and gently fold through until no flour streaks remain.

Add ¼ of the meringue to the pan and mix well to loosen.

Add the remaining meringue and this time, gently fold through until combined and you are left with an even colour.

Transfer the mix to your lined tin and bake for 20 to 22 minutes – anything more will leave the finished cake slightly dry.

Let the cake set and cool in the pan. Once cool, carefully remove and finish the top with a dusting of cocoa powder before slicing with a hot knife.

Top with slightly sweetened whipped cream to finish.