Heat the olive oil and butter in a medium Dutch oven or high-sided skillet over medium heat. Add the leek and cook until tender, 5-6 minutes. Add the garlic and cook for another minute. Stir in the rice and cook for a minute, ensuring the grains are coated in oil. Stir in the wine and cook for a minute or two until it's mostly evaporated. Pour in one cup of the broth along with the salt. Bring to a very low and gentle simmer, stirring constantly, until the rice has absorbed the broth. Add another cup of broth and repeat the process, adding one cup of broth at a time, ensuring the rice has absorbed the liquid before adding the next cup of broth. Add the asparagus and green peas with the 5th and final cup of broth, letting it simmer until the asparagus is tender but with some bite. The rice should likewise be tender but not mushy. Remove the risotto from the heat and stir in the butter, Parmesan cheese and lemon juice. If you prefer a slightly soupier consistency, add a little more broth. Add salt to taste. Serve immediately sprinkled with some chopped chives or parsley and some additional grated Parmesan if desired. Serves 4 as a main dish or 6 as a side dish.