Preheat oven to 400F and line a large sheet pan with parchment paper.
Turn pastry dough out onto a floured surface and roll out into a 8×8 square. Cut dough into 12 squares and arrange in a single layer on prepared sheet pan. Brush squares with egg white wash.
Bake pastry squares at 400F 10-15 minutes until pastry is golden brown. Set pastry squares aside to cool.
Melt butter in a medium pot or Dutch oven over medium-high heat. Add onion, carrot, and celery and cook 3-5 minutes until onion is translucent. Add flour, thyme, and garlic and cook 1-2 additional minutes until fragrant.
Slowly drizzle chicken broth into pot, stirring until evenly incorporated into flour. Add potatoes, turkey, heavy cream, and bay leaf into pot. Season soup with salt and pepper to taste and bring to a simmer over medium-high heat.
Reduce heat to medium-low and allow soup to simmer 10-15 minutes, stirring occasionally until vegetables are tender. Remove and discard bay leaf. Fold peas and parsley into soup and season soup with additional salt and pepper to taste if needed.
Ladle soup into bowls and serve warm with pastry squares for dipping. Enjoy!