Boil 1-1/2 cups chicken broth, scallions, garlic, and a bit of salt and pepper in a covered pan on high for 4 minutes until scallions are soft. Add peas; cover until mixture boils. Cook a minute; add 8 cups chopped fresh spinach and boil until it's tender.
Use a slotted spoon to remove 2 cups of greens mixture. Puree.
Puree rest of mixture and return to pan. Stir in 1/2 cup broth and light cream; heat. Pour into bowls; use a spoon to drizzle plain yogurt into a shamrock shape.