Recipe: A Union Jack Coronation cake fit for your street party

My corner of Camden - bordering West Hampstead and Kilburn - doesn't get much attention or investment. Nor does it have a strong sense of community. The population is rather transient, with renters making for a high churn rate.

I've been here 23 years and have no friends in my street, but when I was delivering leaflets for this event, I met so many neighbours from different parts of the globe. So this is my attempt to make some friends and foster a community feeling in the neighbourhood.

Street parties and lunches will be taking place up and down the country including Kerstin's lunch in Kilburn/West Hampstead (Image: PA)

Tables and chairs, lent by St Cuthberts Church, will line our road and the neighbouring Crescent. Anyone is welcome as long as they bring a dish. If you are a musician, please bring an instrument. Wear red, white, blue, or the coronation colour, purple.

If you want a baking challenge, try this occasion cake using a method called 'biscuit joconde' in French, after the Mona Lisa. The recipe has many steps – it's complicated, but doable even for the amateur. It's also stunning.

A Union Jack Coronation cake (Image: Kerstin Rodgers)

Union Jack Coronation Cake (serves 10)

This cake is not as hard as it looks, and I hope I've explained it adequately with a step by step guide. When you come to serve it, peel away the cake ring carefully. You should see your beautifully patterned Union Jack bavarois cake.

Ingredients:

For the sponge:
85 g ground almonds
75 g icing sugar
25 g plain flour
3 large eggs
3 large egg whites
10 g caster sugar
30 g unsalted butter, melted

For the piping:
200 g unsalted butter, softened
200 g icing sugar
7 egg whites
220 g plain flour
Food coloring in blue and red

Ingredients for the tricolour interior:
1 barquette of raspberries
1 barquette of blackberries
500 ml double cream
100 ml water
12 g of gelatin sheets, silver
250 g caster sugar
Pinch of salt
A few drops of vanilla

Strawberries or blackberries to decorate.

Method:

To make the sponge, whisk the egg whites and white granulated sugar to firm, glossy peeks. Reserve in a separate clean bowl for later use.
Sieve ground almonds, icing sugar, plain flour together.
On medium speed, add the eggs a little at a time to the dry mixture until well combined. Fold in one third whisked egg whites to your mixture to lighten the batter. Then fold in the remaining whisked egg whites until just combined.

Add the melted butter. Cover with cling film and keep the batter to use later.

For the piping decoration:
Beat butter and sugar together until light and fluffy.
Gradually add egg whites. Beat continuously. Fold in sieved flour.
Divide batter into two bowls. They will be red and blue.
Add the coloring until you get your desired shade.
Put the red and blue into separate piping bags.
Then, using a silpat (this is one of the things you really should buy, along with a digital thermometer and a decent peeler) place on a flat baking tray (or turn it upside down), pipe out your Union Jack.
Once you have your design, place the silpat in the freezer for half an hour. I did this twice to have enough length of pattern to surround the cake.

To bake the cake:

Preheat your oven to 250C.

Once your design is frozen, gently spread, using a spatula, the sponge batter over the frozen design in a long rectangular shape. It should be about 3mm thick.
Then bake quickly. It should only take about 15 minutes.
Prepare a rectangle (bigger than the cake) of greaseproof paper dusted with icing sugar.
After 5-10 minutes of cooling flip over your sponge onto the icing sugar dusted paper. You will now see the pattern. Yay!
Using a ruler or a straight metal edge, cut, with a sharp knife, the sponge strip to the height of your bottomless cake mould (I used a springform ring). Straighten the edges too. Place the cake ring on top of a flat sheet of greaseproof paper, and on top of that put a flat sheet of clingfilm. Pull the clingfilm up tightly outside the cake ring.

Cut a length of greaseproof paper to fit inside the cake ring. It should be 1cm taller than the cake ring. Carefully, taking your strip of patterned sponge, line the inside of your cake ring. The pattern should be facing outwards, so that you can see it when you remove the ring. Use the second strip of patterned sponge, pressing the sides together, if one isn't big enough. Cut strips of leftover sponge to fit the bottom.The thin sponge is filled with a tri-colour bavarois (Image: Kerstin Rodgers)

Method for the tri-colour bavarois:

First rub the raspberries into a sieve. This is a pain and you could use raspberry jam, but the acidity of fresh fruit is worth the effort. Keep pushing it through the sieve over a bowl. You'll end up with a lovely seed-free purée. In a separate bowl, do the same with the blackberries. Leave both bowls of fruit purée to the side.

Soak the gelatin sheets in cold water. Combine the sugar and the water in a pan and heat until dissolved. Let it cool. Squeeze out gelatin sheets, add to the sugar syrup. Mix one third into the raspberry purée, one third into the blackberry purée.

Whisk the cream to soft peaks. Mix one third of the cream into the raspberry purée and fold gently until combined. Mix one third of the cream into the blackberry purée and fold gently until combined.

Into the last third of cream, add a few drops of vanilla. Into this also add the last third of gelatiney sugar syrup. Combine, gently.

Into your cake mould, pour the raspberry mixture. Put it in the freezer for 15 minutes. Then pour in the blackberry mixture. Freeze for 15 minutes. Cut the greaseproof paper inside the cake ring level with the top. Lastly, pour in the vanilla mixture. Smooth it out nicely with a spatula. Put the whole cake in the fridge. Allow to set for a few hours.

To Serve:

Peel away the cake ring carefully. You should see your beautifully patterned Union Jack bavarois cake. Decorate with a mix of raspberries and blackberries. You could also use cherries, strawberries and blueberries.