I had never made a sponge and was intimidated by tales of failure.
Then Fury sent me her mum’s recipe. The secret ingredient is boiling water.
(And silence. And sifting the flour twice. But those aren’t really ingredients.)

Recipe from Fury’s mum, Mandy.

Gather:
1/2 cup plain flour
3/4 cup SR flour

4 eggs
3/4 cup caster sugar
60 mls boiling water

To serve:
1 punnet of strawberries
3 tbs icing mixture (or 3 tbs icing sugar + 1 tsp cornflour)

1 cup whipping cream

Then: 

1. Preheat the oven to 180° C. Butter a springform cake tin and line the bottom with baking paper.
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2. For the strawberries: Finely slice the strawberries and add to a small bowl (or container, if you plan to transport and prepare on arrival) with the icing mixture. Stir gently, and allow to macerate for at least a few hours.*
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3. Sift the flours into a medium bowl. TWICE. Set aside.
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4. Separate the eggs, keeping both whites and yolks.
5. In a stand mixer with the whisk attachment (or a large bowl and beat the yolks and sugar until thick and pale (3–4 minutes).
6. Add the boiling water and keep beating until the mixture is thick again (6–8 minutes). Magic!
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7. In a separate large bowl (or after transferring the yolk mixture to a separate bowl and washing the stand mixer whisk and bowl), beat the egg whites until stiff peaks form.
8. Alternating about 1/2 a cup at a time, very gently fold the egg whites and flours into the yolk mixture until everything is incorporated.
9. Spoon the mixture into the prepared tin and bake at 180° C for 35–40 minutes.
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   Do not open the oven. Do not stomp around in the kitchen. Do not make loud crashing noises while doing the washing up.
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   The sponge is ready when it’s (relatively) uniformly golden on top. Do not jab it with a skewer, at risk of deflation.
   
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10. Allow to stand in the tin until half cooled before removing the sides of the tin.** Do not stomp around while the sponge is cooling. It will hear you and probably collapse.
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11. To assemble: Whip the cream (not too much — butter = bad — but thick enough that it will support the top of the cake).***
12. Using a very sharp (or serrated) kitchen knife, slice the cake into two even-height layers.
13. Spread the strawberries in an even layer over the bottom half (you can add some of the juice but not too much — it is a sponge after all). Using a palette knife, spread the cream evenly on top of that. Gently place the top half of the cake on top of THAT. If you have a lot of excess cream, you could add it on top of THAT, but it’s a bit excessive… (I did this.)

Notes:
Obviously this recipe is best suited to those who live alone in large quiet homes, or who can convince their noisy counterparts to be quiet for a while if they want cake later.

*If you’re making this well ahead of time, you can wait until a few hours before cake time to prep the strawberries. Not that they’d suffer from being left to stew in their own juices overnight.
**I made this sponge on a Wednesday night and took it to work the next day. For structural integrity during transport, leave it on the base of the tin until you arrive at your destination.
***If you’re transporting the cake, you can whip the cream and store it in a container in the fridge until you need to move/use it.