For the poblano sauce: Roast the poblanos over a flame until black on all sides (this can also be done under a broiler). Place in a bowl, cover with a lid or plate and set aside for 15 minutes to steam.
Begin the base for the sauce by combining the butter, white onions and garlic in a saucepan. Salt well. Cook over medium heat until the onions are softened, 3 to 4 minutes. Sprinkle with the flour and whisk to combine. Stir in chicken stock, bring to a simmer, stirring, and cook for 1 to 2 minutes, until thickened. Remove from heat and add to a blender.
Peel the blackened skin off the poblanos--this is easier to do under cold running water. Then remove the stems and seeds. Add the flesh to the sauce base in the blender. Blend until smooth, 1 to 2 minutes. Return the poblano sauce to the saucepan and bring to a simmer. Add the cream, starting with 1 cup--add more if necessary. Simmer for 3 to 5 minutes. Season with salt and lemon juice
For the shrimp and crab: In a saucepan, melt the butter over medium heat. Add a pinch of salt and red pepper flakes. Add the shrimp and cook, tossing, until opaque.
Add the crab meat and cook for an additional 2 minutes, stirring well. Check that the shrimp are cooked through and then finish with squeeze of lemon. Set aside.
For the enchiladas: Fry the tortillas for 20 seconds in hot oil to make them pliable. Drain on paper towels. Lay out tortillas and fill with 1 to 2 tablespoons of the seafood filling. Plate 2 enchiladas per serving. Top with poblano sauce and then with queso fresco, Pickled Red Onions and crema. Garnish with cilantro.
Combine the red onions, vinegar, sugar and salt in a saucepan and boil for 30 minutes. Drain the onions. Refrigerate in an airtight container for up to 2 weeks.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.