In a medium saucepan, bring water to a boil.
While water is coming to a boil, spray a nonstick pan with cooking spray and heat pan over a medium flame.
Add mushrooms and kale, and cook appx 8-10 minutes until mushrooms are soft and kale is wilted. Set aside.
When water is boiling, add butter, garlic and couscous. Put lid on pot and reduce to a simmer. Cook for 8-10 minutes.
Turn the heat off and add mushrooms, kale, feta and salt.
Toss well and portion into serving bowls. Garnish with lemon zest.