Soak the tomatoes in a bowl of boiling water until the skin starts to crack. When they are cool enough to handle, peel the skin from them and chop roughly.
In a frying pan dry roast the couscous until it's lightly golden and fragrant. Transfer to a bowl and pour over 1 1/3 cups boiling water. Cover with plastic wrap and leave to sit for 10 - 15 minutes. Remove the wrap and fluff the grain up with a fork. Add the sage and parmesan and stir through.
Heat the oil in a pan and add the eggplant, garlic and tomatoes and cook until the eggplant is tender.
Steam the silver beet for 2 minutes and squeeze out any excess moisture.
Arrange the eggplant mixture in a baking dish and top with the silverbeet.
Place the cous cous mixture over the top. Cover with foil and bake in the oven for 20 minutes. Remove the cover and bake for a further 15 minutes. Serves with a green salad.