Step 1

Preheat oven to 180C / 350F / 160c fan forced. Grease then line a sponge roll (13x9 inch) tin with baking paper. Now grease and flour the baking paper. (notes)

Step 2

Sift together the flour, cocoa, baking powder, baking soda and salt. Mix them well to disperse evenly.

Step 3

Beat the eggs on high for about 2 minutes or until they have doubled in volume, have lightened and look frothy.

Step 4

While still beating, slowly add in the sugar.

Step 5

Add the milk and vanilla and beat well.

Step 6

Turn the beater down to low and tip in the flour, a third at a time until combined. Beat for another 30 seconds on low.

Step 7

Pour the batter into your prepared tin, tipping it from side to side to get it into all the corners and level all over.

Step 8

Bake for 12 to 15 minutes until a toothpick comes out clean.

Step 9

Immediately, use the edges of the baking paper to lift it out of the tin and onto a flat surface. Have the short edge towards you and start to roll.

Step 10

First, tuck in the edge that's closest to you firmly but gently. Peel about one in of the paper away just to release it, then continue rolling the cake all the way up to meet the other end. Firm but gentle is the key.

Step 11

From the end that is hanging out, peel back the paper, then just fold it away from the cake, this just allows the cake to cool better without steaming.

Step 12

Let the cake cool completely before unrolling and adding buttercream.

Step 13

In a stand mixer with a paddle attachment, beat the butter for 8 minutes (yes, that long. We’re going for whipped butter here). Scrape down the sides from time to time and during beating.

Step 14

With the mixer on low, add the sugar 1 spoon at a time until combined. Scrape down the sides of the bowl. Add the salt, vanilla and cream and beat for 5 minutes at medium speed until it looks light and thick and whipped.

Step 15

As soon as the cake is cool,,unroll it very gently (don't try to flatten it out, just unroll enough to add your buttercream). Spread the buttercream over and roll it back up.

Step 16

Roll the cake back up, dust all over with cocoa and serve