Heat the 2 tablespoons oil in a medium heavy skillet over medium-high heat. Add the corn, crawfish, shallots, garlic, salt, and cayenne and cook, stirring often, to heat through and blend the flavors, about 5 minutes. Remove from the heat and let cool.
Beat the eggs in a large mixing bowl. Add the milk, cornmeal, flour, masa harina, baking powder, and Essence and mix well. Stir in the crawfish mixture and mix well.
Heat about 2 tablespoons of the remaining olive oil in a medium heavy skillet over medium-high heat. In batches, drop tablespoons of the batter into the skillet and cook, turning once, until golden brown on both sides, about 2 minutes. Transfer to paper towels to drain.
Serve warm, topping each cake with a spoonful of sour cream and some sliced smoked salmon and caviar, if you wish.
Yield: about 48 cakes