In a non-stick saute pan over medium-high heat coated lightly with extra virgin olive oil add onion and eggplant and season and cook until soft, about 3 minutes.
Add bell peppers and saute until slightly softened, then add tomato, stir and season.
Meanwhile, make couscous: in a large, heat-proof bowl, combine couscous, tamari and 2 tablespoons olive oil and season.
Pour boiling water over and stir quickly to blend and immediately cover bowl with plastic wrap, sealing tightly.
Allow to steam until couscous is tender, about 5-7 minutes.
Fluff couscous with the back of a fork and stir in Thai basil ribbons.
Check flavor and season if necessary.
To serve, using a ring mold or similar, plate couscous in mold on plate and layer ratatouille on top.
Unmold and drizzle with more extra virgin olive oil and garnish with Thai basil sprig, if desired.