How to Make It
In a medium bowl, whisk together the eggs, flour, water, milk and salt. Heat a 7-inch nonstick crêpe pan or skillet over moderately high heat. Pour 2 tablespoons of the batter into the pan, tilting the pan quickly to coat the bottom evenly. Cook the crêpe until lightly browned on the bottom, about 45 seconds. Transfer to a plate and cover with a sheet of wax paper. continue with the remaining batter, layering the crêpes between sheets of wax paper.
Preheat the oven to 400°. Place the boniato in a baking dish and bake for about 30 minutes, or until brown and tender; let the boniato cool slightly. Turn the oven down to 350°.
Meanwhile, bring a large pot of water to a boil. Trim 1/2 inch from each end of the plantain and plunge it into the boiling water. Boil the plantain until tender when pierced at the thickest part, 5 to 7 minutes. Drain well and let cool. Peel the plantain and cut it into 1-inch pieces.
Halve the boniato and scoop out the flesh. In a food processor, combine the plantain and boniato with the cream and puree until smooth.
In a saucepan, melt the butter over moderately high heat. Add the garlic and cook, stirring often, until softened. Add the sherry and bouillon cube and simmer until reduced by half. Add the cream and boil until thickened and reduced to 1 cup. Remove from the heat and add the shrimp and the hearts of palm. Cover and set aside for 10 minutes.
Mound 2 tablespoons of the filling in the center of each crêpe and carefully roll into a cylinder. Arrange the crêpes in a shallow baking dish and sprinkle with 2 tablespoons of water. Cover with foil and bake for about 20 minutes, or until the crêpes are heated through. Rewarm the sauce. Set 1 crêpe on each plate and spoon the sauce on top, making sure to distribute the shrimp and hearts of palm evenly.