Preheat the oven to 180C/355F/Gas 4.
To make the pesto, place the garlic and parsley into a food processor and blend together. With the food processor still running, add the pine nuts, parmesan and oil and blend until smooth. Season, to taste, with salt and freshly ground black pepper.
Skin the tomatoes by cutting a small cross into the bottom and carefully placing them into a heatproof bowl of boiling water for about 30 seconds. Remove them with a slotted spoon and place into a bowl of iced water for one minute. The skin should then peel off easily. Once peeled, slice the tomatoes to the thickness of a pound coin.
Heat a griddle pan until smoking. Slice the courgettes to the same thickness as the tomatoes, season with salt and freshly ground black pepper and place onto the griddle pan to cook for 2-3 minutes on each side, or until striped with griddle marks.
To assemble the salad, place six deep 10cm/4in chefs' rings onto a baking tray. Place a layer of the tomatoes into the bottom of each ring. Season with salt and freshly ground black pepper, then spoon over a little pesto.
Add a couple of basil leaves to cover the pesto layer, then add a layer of feta.
Add a layer of griddled courgette, then repeat the layers of tomato, pesto, basil, feta and courgette.
Top the stacks with a layer of feta and drizzle each with a little olive oil.
Transfer to the oven to bake for 10-12 minutes just to warm the stacks through. (You can then place the stacked chefs' rings under a hot grill to brown the feta if you want.)
To serve, place each chefs' ring onto a plate, and arrange three olives around each stack. Carefully remove the chefs' rings and garnish each Greek salad stack with basil leaves, drizzle with olive oil and place a lemon wedge alongside.