Prep and cook time: about 1 3/4 hours.
1. Stack 1/2 cup spinach leaves and cut into thin slivers.
2. Lay 1 filo sheet flat and brush lightly with butter; cover remaining dough with plastic wrap to prevent drying. Lay another filo sheet onto the buttered piece; brush top lightly with butter. Cut stack into 6 equal squares; cover with plastic wrap. Repeat to make a total of 18 filo squares.
3. Butter 6 muffin or custard cups (2 1/2 to 2 3/4 in. wide; if using a muffin pan, butter alternate cups). Press 3 filo squares into each cup, overlapping, to line the cavity smoothly; filo edges will extend above the rim (in muffin pans, arrange so filo edges don't touch).
4. Sprinkle 2 teaspoons grated parmesan into each filo basket and top with about 1 tablespoon slivered spinach leaves. Break 1 egg into each filo basket, lightly sprinkle with salt and pepper, and sprinkle eggs equally with green onion.
5. Bake in a 350° oven until filo is golden and eggs are softly set when gently shaken, 18 to 20 minutes.
6. Meanwhile, mound remaining spinach equally onto dinner plates. Using a spoon and a small spatula, gently lift egg blossom baskets from baking cups and set 1 on each plate. Add hollandaise to taste. Dust with paprika.