Preheat oven to 220C (425F). In a large bowl, toss the gnocchi with half the oil until coated. Spread out evenly on a baking tray, sprinkle with salt, pepper, and half the butter.
Wash the asparagus and trim the woody part at the bottom, cut into thirds.
Cut the white part of the leek lengthwise and then slice into thin half moons.
Peel the shallot and slice thinly.
Add asparagus, leek, shallot, and the frozen vegetables (if using) to the same bowl and toss with the remaining half of the oil, until coated. Then spread evenly on a different baking tray, sprinkle with salt, pepper and the rest of the butter.
Place both trays in the oven (if placing on different levels, put the gnocchi on the lower, the greens on the higher level) and bake for 20 minutes.
Five minutes into the baking, gently stir the gnocchi to distribute the butter. Do the same with the vegetables. This should be repeated every five minutes for the vegetables ONLY.
Once the 20 minutes are over, take both trays out of the oven, add the gnocchi to the vegetables, sprinkle with the parmesan cheese and toss to mix.
Serve with additional parmesan, if desired, and enjoy!
