Preheat a fan-forced oven to 185 degrees Celsius.

Grease and line a 22 or 23-centimetre springform cake tin with baking paper.

Sift and whisk all dry ingredients together in a large bowl.

In a separate bowl, combine all wet ingredients and whisk until smooth.

Combine wet ingredients with dry ingredients and whisk until smooth.

Pour cake batter into lined cake tin, ensuring you add every last little bit of cake batter with a rubber spatula.

Place in the oven on a middle-level rack and bake at 185 degrees for 30 minutes. Use a wooden skewer to test doneness. It should be slightly sticky when the skewer is inserted into the middle of the cake.

Once cooked, remove cake from the oven and cool for 10 minutes but don’t remove from the cake tin.

Preheat a fan-forced oven to 195 degrees Celsius.

Sift and combine the dry ingredients.

Gently melt butter and chocolate together. Do not heat past 50 degrees.

In the bowl of a stand mixer fitted with a paddle attachment, mix the eggs and brown sugar together on a medium speed until well combined, but do not whip.

Drizzle the chocolate mixture into the sugar mixture with the paddle on speed 1.

Add the dry ingredients into the chocolate and sugar mixture and mix with the paddle on speed 1 until smooth and well combined.

Pour blondie mix onto the top of previously baked vanilla cake and sprinkle the sea salt over the top.

Place the cake tin back in the oven on the centre rack and bake for 40 minutes. It should be set on top but quite gooey on the inside.

Remove the cake from the oven and cool in the tin for 45 minutes.

Cut and serve immediately for a saucy texture or allow to cool to room temperature before cutting for a more set texture.