Preheat the oven to 140C and line a 8 x 8 inch / 20 x 20cm square pan with parchment paper
Combine the milk and butter in a small saucepan over medium heat and heat until the butter has melted and the milk is just steaming
Sift the flour into a large bowl and pour over the hot milk and butter, mix until combined
Add the egg yolks and mix until smooth and well combined, and set aside
In a large bowl add the egg whites and whisk on high speed until foamy with a hand mixer, or in a stand mixer fitted with a whisk attachment
Add the sugar and beat on low speed until the meringue reaches soft to medium peaks
Add ⅓ of the meringue to the egg yolk mixture and mix until well combined
Add the lightened yolk mixture to the remaining meringue and gently use a whisk to fold the mixture until just combined
Transfer the cake batter to the lined cake pan and place it in a larger baking tray filled with hot, but not boiling, water
Bake for 75 minutes or until the cake springs back when touched
Remove from the oven and enjoy warm!
