Set up a blender, a bowl over ice and have a fine sieve ready.
Remove the basil leaves from the stalks and place in a saucepan, cover with olive oil and gently warm to 80'C. Pour into the blender and blend for 20 seconds before passing through the fine sieve into a bowl set over ice.
Cooling it down quickly will help keep a vibrant green colour.
Peel the onion and garlic. Remove the seeds from the chilli and peppers and cut into small pieces. Juice the limes.
Peel the cucumbers and cut 1 into small pieces. With the second cucumber, cut in half lengthways and remove the seeds with a spoon. Cut into small dice. Reserve to garnish the dish.
Score the tomatoes on the base and immerse in boiling water for 10 seconds. Plunge straight into ice cold water. Remove the skin and cut into quarters. Keep half of the tomatoes for garnish.
Add the remaining tomatoes to the other ingredients and blend in a blender until smooth. Pass through a sieve if necessary. Adjust the seasoning with salt, pepper and sherry vinegar. Refrigerate until ready to serve.
With the 3 remaining tomatoes cut into small dices and place in a bowl with the diced cucumber and season with salt and pepper. Chill in the fridge.
Preheat the oven to 200'C.
Fillet the mackerel and then pin bone the fillets using your filleting knife and making a 'v' shaped cut in the centre of each fillet. Cut each fillet into 3cm sized pieces and rub with basil oil and a pinch of salt. Cook in the oven for 2 minutes. Remove from the oven and allow to cool for 2-3 minutes before serving.
Pour the gazpacho into deep bowls and place the mackerel fillets on top. Finish with a drizzle of basil oil and a few remaining Thai basil leaves.
«Rather than making a golden gazpacho use red peppers and red tomatoes instead. Also be experimental with the herbs you use. Lovage would be great in this chilled soup too.»