Combine the chicken stock and diced tomatoes in a saucepan, bring to a simmer and keep at a simmer.
Heat a large Dutch oven over high heat. In a bowl, toss the shrimp with 2 tablespoons of the olive oil, 1 teaspoon of the crushed red pepper and some salt.
Add the shrimp in an even layer to the Dutch oven. Without stirring the shrimp, sear each side hard until golden brown and just barely cooked through, about 2 minutes a side. Transfer the shrimp to a baking sheet.
Lower the heat to medium and add the remaining 3 tablespoons olive oil. Add the onion, some salt and pepper and the remaining 1 teaspoon crushed red pepper and saute until the onion is translucent, about 5 minutes. Add the rice, stir to coat and cook until lightly toasted, about 2 minutes. Add the garlic and saute until fragrant, about 30 seconds. Deglaze with the vodka, scraping the bits off the bottom. Simmer for 1 minute, then add 1 cup of the hot stock mixture and cook, stirring occasionally, until all the stock is absorbed. Continue to cook, adding the stock mixture a ladle at a time, until the rice is creamy but still somewhat firm in texture, 15 to 20 minutes.
Add the shrimp and any accumulated juices to the pan. Add another ladle of the stock mixture, cover and gently simmer until the shrimp is perfectly cooked, 3 to 4 minutes. Add the parsley and butter and stir. Season with salt and pepper. Garnish with more crushed red pepper if desired and serve with grilled bread.