Heat the oil. Peel and finely chop the onion and cook over medium heat for 5 minutes. Wash the aubergine and cut into 1 cm cubes. Add to the onion and fry for about 8-10 minutes. Drain the sun-dried tomatoes and cucumber, chop and mix with the aubergine.
Add the peeled and pressed garlic cloves. Wash the herbs and pat dry. Pluck the leaves from the stems and chop finely. Add mustard, vinegar and capers to the pan and simmer for 5 minutes while stirring.
Put the aubergine mixture in the food processor and puree for a few seconds (the strainer works too). Tastes warm as a starter with baguette or toast, or cold as a spread e.g., at parties.