Strawberry chiffon cake

Method

1. Make a strawberry purée by blending 200g strawberries with a squeeze of lemon juice until liquid. Pass the mixture through a fine strainer to remove any pips.
2. Heat the oven to 160°C fan/gas 4. In a large bowl, sift together the flour, cornflour, baking powder and salt.
3. In another bowl, beat the egg yolks with an electric hand whisk and ⅓ of the sugar until they are thick, pale and hold a ribbon trail for 3 seconds. Stir in 1 tbsp lemon or lime zest, the juice of 1 lemon (about 40ml) and 140ml of the strawberry purée. You can also add a drop of red food colour and/or vanilla extract at this point if you have it. Beat in the oil until incorporated.
4. In another large bowl, whisk the egg whites in a stand mixer or with a hand mixer until very white and foamy. Gradually add the remaining sugar one spoon at a time, beating until it reaches stiff peaks (when you lift out the beaters the tips of the peaks formed don’t flop over).
5. Use a spatula or metal spoon to gently mix the dry ingredients into the egg yolk mixture a little at a time until  just combined. Gently fold in spoonfuls of the egg whites, ensuring they’re as fully incorporated as you can. The mix will be voluminous and look like a big fluffy pink milkshake.
6. Scrape the cake mixture into the ungreased cake tin and bake for 35-40 minutes. Test by lightly pushing with the pad of your finger and to see if it feels a little bouncy. Invert the cake tin to cool upside down on your worktop. (An angel tin comes in handy here, as it has its own little feet, but if not, prop your upside-down tin on top of few cans of food to keep it upright.)
7. Meanwhile, make the icing: put the remaining strawberry purée (about 1 tbsp) in a bowl with the soured cream, then sift over 300g icing sugar and stir together. You can add a bit more icing sugar if needed. You want it to be thin enough to spoon over the cake but not so thin it dribbles off completely.
8. Once cool (about 30 minutes), turn the cake back upright and carefully release the cake from the tin. Resting your hand on the centre of the tin, ease a sharp, flat knife between the cake and the tin, ensuring you hit the tin’s base. With the knife at an angle so the blade is at the side of the tin, gradually drag the palette knife around the cake, in a firm, smooth and confident motion, releasing it from the sides of the tin.
9. Cover the cake with the thick pink icing, start by drizzle the icing around the edges of the cake and then you can watch how it pours along the sides and judge how much icing you need to add. Gently smooth it around with a spatula. You can decorate the cake with the remaining strawberries, thinly sliced and the lime zest. Once the icing is dry-ish, serve the cake in slices.