Heat oven to 350 degrees. Sauté asparagus tips, leeks and artichokes in olive oil over medium heat just until crisp-tender, approx. 2 min. Cool.
Combine eggs, ricotta, Pecorino, 3/4 c feta, cream and herbs. Line sheet pan with parchment paper and spray pan lightly with olive oil spray.
On work surface, lay one sheet of phyllo out and spray top with olive oil; transfer to sheet pan, sprayed side up, pressing sheet gently into place (small wrinkles or air pockets around edges are actually desirable for a rustic, crisp crust). Repeat with remaining sheets, spraying one side and gently placing into pan, sprayed side up. When all 8 sheets have been layered, pour filling into pan and spread evenly. Add cooked vegetables, pressing into filling, topping with 1/4 c feta.
Bake 45 min, until puffed in the center and golden brown on the edges. Remove from oven and cool at least 10 min before slicing. Garnish with fresh chopped chives.