The mild heat of roasted poblano chiles is nicely balanced by a stuffing of cornmeal, potato, and shrimp.
Roast poblanos over a high flame or under a broiler, turning frequently, until lightly charred on all sides, about 1 minute per side. Place in a bowl; cover with plastic wrap for about 15 minutes. When cool enough to handle, remove charred skin by rubbing with a paper towel, being careful not to tear the flesh. Cut a lengthwise slit down poblanos, and use a pairing knife to remove the seeds, leaving the stem intact. Set aside.
Heat oven to 350 degrees. Shell and devein the shrimp. Set aside six shrimp. Remove the tails from the others; cut them into 1/2-inch pieces. Set aside.
Place a large saute pan coated with olive-oil cooking spray over medium heat. Add garlic, and saute until translucent. Add potatoes and red, yellow, and jalapeno peppers; stir to combine. Add 1/2 cup water. Increase heat to high, cover, and cook until potatoes are tender, about 5 minutes. Remove lid, and continue cooking until all the liquid has been absorbed. Stir in chopped shrimp, corn, epazote, salt, and pepper. Saute until shrimp are cooked through, about 5 minutes. Remove from heat, and set aside.
Place chicken stock in a small saucepan. Squeeze lime into stock, add halves, and bring to a broil. Add whole shrimp; cook until opaque and bright pink, about 2 minutes. Remove shrimp and limes from stock, set aside shrimp, and discard limes. Add cornmeal to stock mixture in a fine stream, and reduce heat to low. Cook, whisking occasionally, about 5 minutes. Add to chopped-shrimp mixture; stir to combine.
Fill each chile with about 3/4 cup shrimp mixture. Place on a baking sheet coated with olive-oil cooking spray, and cook in oven until heated through, about 20 minutes. Top each poblano with a shrimp, and serve with roasted-tomato-pepper sauce.
If you can't find fresh poblano chiles, substitute canned whole poblanos, and skip step one.