Chicken and Vegetable Pot Pie

Ingredients

• 50g butter
• 1 onion, or leek finely chopped
• 1 carrot finely chopped
• 2 sticks celery, finely chopped
• 2 cloves garlic, crushed
• 2 T flour
• 2 cups chicken stock, heated
• 2 tsp Dijon mustard
• ½ cup crème fraiche
• 2 tbsp chopped fresh herbs or 1 tsp dried tarragon
• 600g sliced Hellers chicken
• 150g frozen spinach, thawed
• salt and pepper
• 1 sheet of butter puff pastry (use two if your pie dish is bigger)
• 1 egg, beaten for egg wash