Chicken and Vegetable Pie (Cooking on a Budget)

Ingredients

• 1/4 cup butter
• 2 tbsp flour
• 1 cup prepared chicken stock
• 1/4 cup milk
• 1 coarsely chopped onion
• 2 sliced carrots
• 2 sticks celery, sliced
• 500g/1lb cooked chicken, cubed (Use leftover chicken, another meat of your choice or omit for a vegetarian pie)
• 1/2 cup fresh or frozen peas
• 1 egg, beaten for glazing
• salt & black pepper