To help keep cooks happy before dinner is served, offer this appetizer. Make the sauce up to three days in advance and refrigerate. To save time, you can use four bottled roasted bell peppers instead of roasting your own. Prepare the shrimp — or buy precooked — the day of the party.
Cut bell peppers in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 15 minutes or until blackened. Place in a zip-top plastic bag and seal. Let stand 15 minutes. Peel peppers. Place bell peppers, sour cream, and next 6 ingredients (sour cream through garlic) in a food processor; process until smooth, scraping sides of bowl occasionally. Place bell pepper mixture in a small bowl. Cover and chill. Bring 6 cups of water to a boil in a Dutch oven. Add shrimp; cook 3 minutes or until done. Drain and rinse with cold water; peel. Cover and chill shrimp. Serve shrimp with sauce.