Combine the parsley, mint, lemon zest, and minced garlic in a small bowl and set aside for the final garnish.

Bring the chopped asparagus ends, dark green leek parts, herb stems, broth, and water to a boil in a large saucepan over high heat. Reduce the heat to medium-low, partially cover, and simmer for 20 minutes to infuse the liquid. Strain the broth through a fine-mesh strainer into a bowl, pressing firmly on the solids to extract as much liquid as possible, then return the strained broth to the saucepan and keep it warm over low heat.

Melt a tablespoon of the butter in a Dutch oven over medium heat. Add the asparagus spears and a pinch of salt and pepper, cooking until the asparagus is crisp-tender and bright green, about 4 to 6 minutes. Stir in the peas and cook for 1 minute more before transferring all the vegetables to a plate.

Melt three tablespoons of butter in the empty Dutch oven over medium heat. Add the white and light green leek parts, garlic, salt, and pepper, cooking until the leeks are softened and translucent, 5 to 7 minutes. Stir in the rice and cook, stirring frequently, until the edges of the grains begin to turn translucent, about 3 minutes.

Stir in the wine and cook until it is fully absorbed by the rice. Pour in four cups of the hot broth mixture, reduce the heat to medium-low, cover, and simmer until the liquid is almost entirely absorbed and the rice is just al dente, about 18 to 19 minutes, stirring only twice during the process.

Add a half-cup of the remaining hot broth and stir gently and constantly until the risotto becomes creamy, about 3 minutes. Stir in the Parmesan, remove the pot from the heat, and let it rest, covered, for 5 minutes. Fold in the lemon juice, the remaining tablespoon of butter, and the cooked asparagus and peas. Adjust the consistency with any remaining broth until the risotto is loose and saucy, then serve immediately topped with the gremolata.