Savory Blue Cheese, Leek and Walnut Hand Pies

Name: Savory Blue Cheese, Leek and Walnut Hand Pies
Prep time: 1 h 30 min
Total time: 1 h 30 min
Cuisine: European, British
Ingredients: 2 leeks, chopped (white and pale green parts only); 15 grams unsalted butter (1 tablespoon), for caramelizing the leeks; 2 sheets of puff pastry, thawed according to package directions if frozen; 125 grams blue cheese (4 1/2 ounces), crumbled; 40 grams walnuts (1/3 cup), coarsely chopped; Salt and pepper, to taste; 1 egg, lightly beaten; Fresh thyme leaves, to garnish