Two and a half years ago, Petra Barran, 32, bought an an ice-cream van on e-Bay and converted it into Britain's first mobile chocolate bar. She enlisted decorative help from international graffiti artist Insa and bought Venezuelan supplies from Willie of Channel 4's Wonky Chocolate Factory fame.

Barran begins her "big chocolatey tour" of Britain on April 10 in Essex ("What better a place to begin, hey?"), curving round to Kent and the Home Counties clockwise in the first three-week phase.

Her aim is to explore British food communities in all their diversity and richness by visiting markets, farms, schools and producers.

"I've decided to do the trip in three big swirling sweeps of the land. I'm looking for people to invite me into their homes for supper, in exchange for me bringing the (chocolate) pud - and if there's somewhere to pitch my tent and plug the van in overnight then all's the better."

Follow Petra's tour at chocstar.co.uk and read regular updates at timesonline.co.uk/realfood

Share her (no longer) secret recipe for: CHOCOLATE GUINNESS CUPCAKES

These cakes always attract a lot of attention on the countertop – and cries of amazement that they actually have Guinness in them.

CUPCAKES

250ml Guinness
250g slightly salted butter
80g cocoa
400g caster sugar
1 x 142ml pot sour cream
2 eggs
1 tablespoon vanilla extract
270g plain flour
21⁄2 teaspoons bicarbonate of soda

CREAM CHEESE FROSTING

300g cream cheese
150g icing sugar
150ml double cream

METHOD

Preheat the oven to 180°C/gas mark 4. Line 2 X 12 hole muffin tins with large muffin cases. Pour the Guinness into a large saucepan, add the butter in small pieces and heat until it all melts together. Turn off the heat but leave the pot on the pan.

Whisk in the cocoa and sugar. Beat together the sour cream, eggs and vanilla extract then mix into to the pan. Finally whisk in the flour and bicarbonate of soda. Do this little by little so you avoid lumps of flour in the batter.

Now divide the mixture between the muffin tins – I use a piping bag because the mix is pretty wet. If no bag then a jug works fine.

Place tins in the oven and bake for 18-20 mins, or until they are nicely puffed up and a skewer comes out clean (not looking like it's dragging half the mix with it).

Cool on racks and remove the cakes from the tins when they're firm/cool.

For the icing put the cream cheese, icing sugar and cream into a bowl. Mix together slightly so the icing sugar doesn't blow all over the place when whisking. Whisk with an electric whisk until you get a good, thick consistency and there's no danger of the icing dripping over the sides of the cupcakes.

Ice the cakes – nice big, billowing slathers to give the illusion of a small, sweet, edible Guinness.

Eat whenever you're ready but there's nothing quite like a warm cupcake topped with the cool frosting….

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