Start by preparing the vegetables. Boil a medium sized pot of water, and have ready a large bowl of ice water. Thoroughly wash the fiddlehead ferns, then rub them in a kitchen towel to remove any of the brown paper-like chaff. Cut off any brown tips or blemishes. Rinse again if necessary.
Blanch both the asparagus and fiddlehead ferns for about 2 minutes, until bright green, then plunge into the ice water bath to stop the cooking. Set aside.
Bring the broth to a simmer, then cover and keep warm over medium-low heat.
In a large heavy-bottomed pot, heat the oil and 1 1/2 tablespoons of butter over medium-high heat. Add the leeks, scallions, and garlic, and saute until tender and almost translucent -- about 5 minutes.
Add rice, and stir until grains are translucent at their edges but still opaque in the center, about 3 minutes. Add wine, and stir until liquid is almost completely absorbed. Add the warm stock by the cupful, stirring until rice has absorbed nearly all of the liquid before adding the next cup.
When rice is almost done (about 15 minutes), stir in the blanched and drained vegetables and the lemon zest. Stir in the last 1/2 cup of stock, then add the cheese and remaining butter.
The risotto should be creamy and tender, and the vegetables cooked but with a remaining firm bite. Serve immediately.