Chef Rick Bayless shares his recipe for this elegant Mexican dish.
Preheat the oven to 350 degrees. Spread the almonds on a small rimmed baking sheet, and toast until golden (but not browned), and fragrant, about 10 minutes. Cool, and set aside. Reserve a scant 1/4 cup for garnish.
In a saucepan, heat 1 1/2 tablespoons oil over medium heat; add onion, garlic, and chiles. Cook, stirring frequently, until translucent, about 3 minutes. With a slotted spoon, transfer to the jar of a blender. Set the saucepan aside. Add the almonds, tomatillos, radish leaves, 1/2 cup cilantro, parsley, and 1 cup stock. Blend until smooth.
Add 1 tablespoon oil to the saucepan, and place over medium-high heat. When oil is hot, add the puree. Cook, stirring, until mixture darkens slightly and thickens considerably, about 10 minutes. Stir in remaining 2 cups stock, reduce heat to medium low, and simmer until thick enough to coat the back of a spoon, about 20 minutes. Working in batches, return sauce to the jar of a blender, and puree until very smooth, keeping blender cap covered with a clean kitchen towel to avoid splattering. Return to saucepan, and season with salt.
Just before serving, turn oven on to lowest setting. Season shrimp generously with salt, tossing to coat evenly. In a large heavy skillet, heat 1 tablespoon oil over medium-high heat. When hot, add half the shrimp in a single layer. Cook until milky white underneath, about 1 1/2 minutes. Turn, and cook 1 minute more; do not overcook. Sprinkle with 2 tablespoons cilantro, and toss to combine. Transfer to a plate, and keep warm in oven. Repeat with remaining shrimp and cilantro, adding more oil to the pan if necessary.
Roughly chop reserved almonds. Ladle a portion of the sauce onto each of six warm dinner plates. Arrange shrimp over sauce, and garnish with a few leaves of parsley and a sprinkling of reserved almonds. Serve immediately.