Preheat the oven to 220C/425F/Gas 7.
For the relish, heat the olive oil in a saucepan and gently fry the shallot and garlic. Season with black pepper, salt and ground cumin. Add the white wine vinegar and simmer until the volume of liquid has reduced a little. Add the tomatoes, cover with a lid and simmer for 45-50 minutes, or until you have a thick relish consistency.
For the tart, line a flat baking sheet with baking parchment.
Cut out four 16cm/6Â¼in rounds from the puff pastry sheets (use a 1 litre/1Â¾ pint pudding bowl as a guide). Mark a 15mm/Â¾in border in the pastry circles (use a 500ml/18fl oz bowl as a guide). Place the pastry on the prepared baking sheet and prick the centres with a fork.
Spoon some of the cooked relish into the centre of the pastry circles. Arrange the slices of plum tomato on top and brush the border with beaten egg - making sure you donâ€™t brush the cut edge as this will prevent the pastry rising. Bake in the oven for 20 minutes, until the pastry is risen and golden-brown.
Meanwhile make the herb oil. In a pan, gently heat the garlic in the olive oil with the basil stalks and tarragon stalks. Remove from the heat after 10 minutes and season with salt and pepper.
Place a small handful of the basil leaves, tarragon leaves and watercress leaves in a small food processor (reserve the rest for the salad). Pour over some boiling water to wilt the leaves. Drain the water from the food processor and blend the leaves to a paste. Pour in the herb-infused oil and blend again until smooth.
Make a salad with the remaining watercress, basil and tarragon leaves. Season with salt.
To make the tapenade, blend the olives, capers, anchovies, parsley, brandy and black pepper together in a small food processor. Loosen with a little olive oil and blend to make a paste.
Serve the cooked tarts topped with a small quenelle of tapenade and some herb salad. Drizzle with the herb oil.