All my preconceptions about Mexican food were blown out of the water on my first trip to the country, when I discovered a cuisine that offers everything from butch street food to incredibly refined dishes, from hearty food like grandmother’s mole to delicate crab soups.

I love to explore street stalls and local places to eat rather than posh restaurants and, while I was in Mexico City, I had two extraordinary experiences.

On every street corner there were people selling fresh fruit with chilli powder on. Long chunky fingers of water melon – with the skin cut off – were on sale dusted with salt and very finely powdered chilli and lime. When you are all sweaty and grimy in the heat of the city, this is the most delicious and refreshing thing ever – and super cheap.

The other total eye-opener was at a taquería on the outskirts of the city. It was a taco house, but the tacos weren’t like anything I have ever experienced. My friend, who lives in Mexico, ordered for me and I tucked into something that was so incredibly tasty – “tender and giving” was how I described it. I couldn’t guess what it was. It turned out to be pig’s vagina! It had been gently braised and was served with diced raw onions and fresh coriander leaves on a corn taco.

I had eaten bull’s balls before, but I’d had never tried anything like this. It was a bit of a surprise to learn what it was, but I’m not squeamish – I just asked for another!
• Valentine Warner is an ambassador for Earth Hour 2015, where people all over the world are asked to turn the lights out for the sake of the planet. It takes place at 4pm GMT on Saturday 28 March