1. Place bell peppers directly on a gas-stove burner over high heat, turning with tongs as soon as each side is blistered and blackened. (Alternatively, roast peppers under the broiler.) Transfer to a bowl; cover with plastic wrap. Let stand until cool enough to handle. Peel peppers, discarding skins; cut in half, and discard seeds and ribs. Transfer peppers to the bowl of a food processor fitted with the metal blade. Puree until smooth; set aside.

2. Heat 2 tablespoons oil in a large skillet over medium heat. In a large bowl, toss shrimp with 3/4 teaspoon salt, and season with black pepper. Arrange a third of the shrimp in a single layer in skillet. Cook until they are opaque and cooked through, 3 to 4 minutes, turning once. Transfer to a plate; repeat with remaining oil and shrimp, wiping out skillet with paper towels between batches, as needed. Set aside; cover loosely to keep warm.

3. In same skillet, melt 2 tablespoons butter over medium heat. Add zucchini and remaining 1/4 teaspoon salt, and season with pepper. Cook until zucchini is just tender and bright green, 3 to 4 minutes. Remove from heat; set aside.

4. Place stock in a large saucepan over medium heat. Add shrimp shells, and bring to a boil. Remove from heat, and strain through a fine sieve, discarding shells. Return stock to pan, and bring back to a boil; keep at a low simmer.

5. Meanwhile, melt 6 tablespoons butter in a large heavy-bottomed saucepan over medium heat. Add shallots, and cook, stirring constantly, until they are soft and translucent, about 4 minutes. Add rice; cook, stirring constantly, until grains are glossy and make a sound like glass beads clicking, 3 to 4 minutes.

6. Add the wine to rice mixture. Cook, stirring constantly, until wine is completely absorbed by the rice.

7. Using a ladle, add about 3/4 cup hot stock to the rice along with a few tablespoons reserved pepper puree. Stir constantly with a wooden spoon at moderate speed until mixture is just thick enough to leave a clear wake behind spoon; be careful not to stir too vigorously, or mixture may become gluey.

8. Continue adding hot stock 3/4 cup at a time along with some puree, stirring constantly, until rice is mostly translucent but still opaque in the center, a total of 18 to 25 minutes. As rice nears doneness, watch carefully to make sure it does not overcook. You may not need to use all of the stock and can add smaller amounts as you go along. The final mixture should be thick enough to suspend the rice in liquid that is the consistency of heavy cream.

9. Remove from heat, and stir in reserved shrimp and zucchini, remaining 2 tablespoons butter, and the basil. Season with salt and black pepper, and garnish with basil, if desired. Serve immediately.