How to Make It
Heat vegetable oil in a small saucepan over medium. Add pepitas; cook, stirring and tossing often, until slightly puffed and toasted, about 3 minutes. Let cool slightly, about 5 minutes.
Combine parsley, 1/4 cup olive oil, lemon juice, oregano, salt, garlic, crushed red pepper, and cooled pepitas in a blender. Process on medium speed, slowly drizzling in remaining 1/4 cup olive oil, until mixture is slightly smooth yet still textured, 20 to 30 seconds.
Transfer mixture to a container with a tight-fitting lid. Set aside at room temper-ature until ready to use (up to 3 hours). (Pistou can be stored in an airtight con-tainer in refrigerator up to 2 days; bring to room temperature and stir before using.)
Heat oil in a medium stockpot over high. Add onion; cook, stirring often, until softened, about 5 minutes. Add pumpkin and stock; bring to a boil over medium-high. Reduce heat to medium- low, and add thyme. Simmer, uncovered, until pumpkin is fall-apart tender, about 30 minutes. Remove stockpot from heat. Remove and discard thyme; stir in cream.
Working in batches if needed, pour soup into a blender. Secure lid on blender, and remove center piece to allow steam to escape. Place a clean towel over opening. Process on high speed until smooth, about 30 seconds. With blender running on medium speed, gradually add butter; process until silky-smooth, 1 minute and 30 seconds to 2 minutes. Transfer soup to a clean large pot; stir in salt.
Ladle soup evenly into 4 bowls. Top each bowl with about 2 tablespoons pistou.