In a heavy soup pot, heat 1 tablespoon of the oil over medium heat.  Add the leeks and oregano.  Cook, stirring occasionally, until the leeks begin to wilt, about 4 minutes.
Add 4 cups of water (or fish stock or clam broth) and the potatoes.  Bring to a boil over high heat.  Add the quinoa.  Boil uncovered over medium-high heat for 10 minutes.
Meanwhile, in a food processor or blender, process 3 cups of the corn kernels (defrosted) with 1 cup of water to create a coarse puree. 
After the quinoa has cooked for 10 minutes, stir in the corn puree and remaining corn kernels.  Adjust the salt and add lots of freshly ground black pepper.
Continue cooking until the quinoa is done (the grains should be translucent and have no opaque white dot in the center), about 2 to 3 minutes more.  
Add shrimp, and cook until shrimp turn pink, about one minute. Stir in the cilantro, scallion greens and additional tablespoon of oil.
Add enough lime juice (to taste) to sharpen the flavors.

Garnish with popcorn and pass additional popcorn in a bowl at the table (optional).