How to Make It
In a large saucepan, bring the water to a boil with a pinch of salt. Whisk in the grits and cook over moderate heat, stirring often, until the grits are tender and very thick, about 15 minutes. Stir in the cheese and butter and keep warm.
Meanwhile, thread the jalapeños onto skewers. Roast them along with the poblanos over a gas flame or under a broiler as close to the heat as possible, until blackened, about 3 minutes. Transfer to a bowl and let cool for 10 minutes, then rub off the skins under running water. Stem and seed the chiles.
In a small saucepan, cook the garlic in the olive oil over moderate heat, stirring, until the garlic is softened and very lightly browned, about 5 minutes. Using a slotted spoon, transfer the garlic to a blender. Add the chiles and the orange juice and puree until smooth. Add all but 2 tablespoons of the garlic oil and puree until creamy. Season the sauce with salt and pepper.
Toss the shrimp with the remaining 2 tablespoons of garlic oil. Heat a very large skillet until very hot, about 2 minutes. Add the shrimp in a single layer and cook until browned and just cooked through, about 1 minute per side.
Spoon the grits into bowls and top with the shrimp. Spoon the chile sauce all around and serve.