Spring Vegetable Risotto

Name: Spring Vegetable Risotto
Ingredients: 6 cups chicken stock, homemade or low-sodium canned; 1 tablespoon butter; 6 ounces shitake mushrooms, cleaned and sliced; 2 tablespoons olive oil; 2 large leeks, white and pale green parts only; 3 cloves garlic, chopped; 2 cups Arborio rice; 1 cup dry white wine; 1 pound asparagus; 10 ounces frozen peas, defrosted or about 1 ½ cups shelled fresh peas; 1 small bunch fresh baby spinach, trimmed (about 1 cup); Zest from 1 lemon; 3/4 cup grated Parmigiano or Pecorino, plus additional for shaving; Salt and freshly ground pepper, to taste