Place the sun-dried tomatoes into a bowl with the water. Soak for 30 minutes, until rehydrated. Drain in a sieve over a bowl, reserving the water, and roughly chop the tomatoes.
Place a medium saucepan over a medium heat. Add the reserved sun-dried tomato water and bring to the boil.
Add the couscous and stir in. Remove the saucepan from heat, cover with a lid and allow to sit for five minutes, until liquid has been absorbed by the couscous. Gently fluff the couscous with a fork.
Meanwhile, heat the olive oil in a shallow pan. Add the chopped sun-dried tomatoes, garlic, and spring onions and sauté for five minutes, until the spring onions are tender.
Add the basil and lemon juice and season, to taste, with salt and freshly ground black pepper.
Add the mushrooms and continue cooking for 3-5 minutes, until browned and cooked through.
Add the mushroom mixture to the couscous, stir through to mix well and serve.