Shrimp in pumpkin-seed sauce Prep: 25 minutesCook: 29 minutes Makes: 4-6 servings For Cinco de Mayo, food writer Bill Daley reported on sauces to accent the celebration. This recipe, published in "Recipes From the Regional Cooks of Mexico" and "Nothing Fancy," is cookbook author Diana Kennedy's version of a sauce from Tampico in the Mexican state of Tamaulipas, along the Gulf of Mexico. 1 1/2 pounds medium shrimp, peeled, shells reserved 2 1/2 cups water Salt 1 cup hulled pumpkin seeds, unroasted, unsalted 3 serrano chilies 1/4 medium white onion, chopped 8 sprigs cilantro or more to taste 2 tablespoons butter 2/3 cup creme fraiche or sour cream 1. Put shrimp shells, water and salt to taste in a saucepan; cook over medium heat, 15 minutes. Strain, reserving broth; discard shells. Heat shrimp in broth to a simmer; cook, 2 minutes. Strain, reserving the broth. Set shrimp aside. 2. Lightly toast pumpkin seeds in a dry skillet. The seeds should puff up a little but not brown. Puree the broth, pumpkin seeds, chilies, onion and cilantro in a blender until smooth. 3. Melt butter in a saucepan over low heat; stir in the sauce. Cook, stirring occasionally, about 10 minutes. If the sauce becomes lumpy, return to blender; blend until smooth. Stir in the creme fraiche and shrimp; heat through.