Preheat oven to 350 F. Fold a large piece of parchment paper diagonally in half to crease it. Open, and lay it flat.
Using a mandolin, thinly shave shallots, asparagus, green garlic, and fennel. Slice lemon. Add green peas. Combine all the vegetables together and lightly toss in olive oil, salt,
and pepper.
On one side of the fold, place the vegetables. Place salmon on top. Drizzle with lemon juice and olive oil, and season with salt and pepper.
To close, fold parchment over salmon. Fold edges over and crease, in order to create a sealed half-moon-shaped pouch. Place on a rimmed baking sheet. Bake until salmon is opaque, 9-12 minutes.
While the packet is cooking, combine Greek yogurt, lemon juice, fennel fonds, salt and pepper.
Remove pouch from oven, open carefully, finish with fresh pea sprouts and serve with yogurt sauce.