Pre-heat oven to 200 degrees F. Set wire rack in rimmed baking sheet and place in oven on rack set at middle position. Place a colander inside medium bowl and set aside
Melt 1 tablespoon butter in a 12-inch nonstick skillet over medium heat. Add shrimp and cook stirring frequently, for about 2 minutes. Transfer all shrimp to the colander to drain
Return skillet to heat and add remaining 2 tablespoons butter. Add poblano, serrano, onion and cook, stirring frequently, until vegetables are softened and beginning to brown. Stir in garlic, oregano, coriander, cumin, and salt and cook for 1 minute. Add tomatoes and cook until the vegetable mixture is dry, about 4-5 minutes. Remove from heat and stir in cilantro.
Transfer the drained shrimp to the vegetable mixture, discard the juices, and stir to combine. Season with salt to taste. Wipe skillet clean with a paper towel.
Stack tortillas, wrap in a damp dish towel, and place on a plate. Microwave for about 30 seconds until warm and pliable. Place 1 tortilla on baking sheet (keeping others covered) and brush top lightly with oil. Flip tortilla over, then sprinkle evenly with ¼ cup cheese. Spread ¼ cup shrimp mixture over half of the tortilla, leaving a 1/8-inch border at edge. Fold and press the tortilla to close. Repeat with remaining tortillas, oil, and filling.
Arrange 4 tacos in empty. COLD, skillet with open sides facing toward the center of the pan. Place skillet over medium-high heat and cook until cheese has melted and tacos are browned on 1 side, 2-3 minutes. Using a thin spatula, carefully flip tacos. Cook until browned on the second side, 2-3 minutes. Adjusting heat as necessary.
Remove skillet from heat and transfer tacos to prepared sheet in oven to keep warm. Arrange the remaining 4 tacos in skillet and return pan to medium-high heat to cook. Serve immediately, passing lime wedges, crema, and cilantro separately. Open tacos to add garnish.