In a large heavy bottomed pot, heat olive oil over medium high heat. Sauté onions for 5 minutes or until translucent. Add garlic and rice and cook 2 minutes, stirring to coat rice in oil. While continuously stirring, add 1/2 cup of stock at a time. Simmer and stir constantly and allow each 1/2 cup to be fully absorbed before adding more. Once all the stock has been incorporated, add mushrooms and cook 3 minutes more or until mushrooms wilt just a bit. Remove from heat and stir in cheese, salt, zest and pepper.

In a large bowl, combine spinach, cheese and walnuts. Toss with dressing and serve with risotto.