Trim the ends from the asparagus. Cut the remaining stalks into 1-inch pieces.
Bring a medium pot of salted water to a boil and add the asparagus. Cook until crisp tender, 3-4 minutes. If using fresh peas, add the peas along with the asparagus. If using frozen peas, add them during the last minute.
Transfer the vegetables to a bowl of ice water. Drain the vegetables and set aside.
Heat the stock along with water in a large saucepan. Add the trimmings from the asparagus and leek and the parsley stems to add flavor to the stock. Bring to a simmer and then keep warm on low heat while you make the risotto.
Heat the oil in a large, wide sauté pan over medium heat. Add the leeks and garlic and season them with salt and pepper. Cook until leeks are partially softened, 4-5 minutes.
Add the rice and stir to coat all of the grains with the oil. Cook 1-2 minutes to lightly toast the rice and then add the wine. Cook a few minutes until the wine is reduced, stirring occasionally.
Add the warm stock, a few ladles at a time, stirring the rice frequently. Each time the liquid is almost completely absorbed, add some more stock. Continue adding the liquid in this manner, stirring often, to develop the starch in the rice. It should take about 20 minutes for the rice to cook once you start adding the liquid.
When the rice is done, it will be plump and al dente- tender but still firm to the bite. At this point, lower the heat and stir in the lemon juice and zest, asparagus, peas, parsley, parmesan cheese, 1 teaspoon salt and ¼ teaspoon pepper.
Stir to combine all ingredients well. Taste and adjust seasoning with salt and pepper as needed. Garnish with parsley and lemon zest. Serve hot.