This comforting creamy turkey soup is a great way to repurpose your Thanksgiving leftovers. The vegetables are perfectly tender and the broth is creamy and flavorful—a perfect soup for when there's a chill in the air!
Melt butter and oil in a large pot oven over medium heat. Add leek, carrots and celery; cook, stirring occasionally, until softened, 6 to 8 minutes. Add garlic and thyme; cook, stirring constantly, until fragrant, about 1 minute. Stir in flour; cook, stirring constantly, until the vegetables are coated in flour, about 1 minute. Stir in broth, milk, potato, salt and pepper.
Increase heat to medium-high and bring to a boil, stirring until the liquid thickens slightly, about 1 minute. Reduce heat to medium and simmer, partially covered, stirring occasionally, until the potatoes are tender, about 15 minutes.
Stir in turkey and peas. Simmer until warmed through and the peas are bright green, about 2 minutes. Sprinkle each serving with celery leaves, thyme and ground pepper, if desired.
Refrigerate in an airtight container for up to 5 days or freeze for up to 3 months.