In a large, deep saute pan or pot, heat the olive oil over medium-high heat. Add the chorizo and cook until browned and the fat is rendered, about 3 minutes. Add the onions and shallots and cook for 2 minutes. Add the garlic and cook for 30 seconds. Add the salt, black pepper, red pepper flakes, and stir to combine. Add the shrimp stock and bring to a boil. Add the clams, potatoes, tomatoes, green onions, cilantro, and Essence. Cover and cook until the clams open, about 5 minutes, shaking the pan occasionally.
Remove from the heat and discard any unopened shells. Garnish with the parsley and either serve directly from the pot at the table, or ladle into large soup bowls. Serve with hot, crusty Portuguese bread.
Combine all ingredients thoroughly and store in an airtight jar or container.
Recipe from "New New Orleans Cooking", by Emeril Lagasse and Jessie Tirsch. Published by William and Morrow, 1993.