Wash and spin all herbs. Pick leaves from stems (small stems are fine) and lay the herbs out between two layers of paper towel or two clean tea towels. Roll up and refrigerate until needed (you want them as dry as possible).
Split the green chili lengthwise, remove seeds and white membrane. Roughly chop.
Zest (optional) and juice lemon.
Halve the avocado, deseed and remove from skin. Roughly chop and sprinkle well with lemon juice.
Add garlic, anchovies, capers, chili, 1 teaspoon sugar and a pinch of salt to the food processor. Pulse until very finely chopped (don’t scrape down).
Add avocado, mayonnaise, yoghurt and herbs (I snip chives into small batons) and pulse, scraping down several times in this step, until herbs finely chopped and sauce well combined.
Taste and adjust seasoning with pepper, salt, lemon juice and sugar. Don’t feel you need to use all the lemon juice.
Empty into a sealed container and refrigerate until required.