Chicken and vegetable pie

Ingredients

• 45 gram butter
• 2 tablespoon olive oil
• 2 leeks - finely diced, green leaves discarded
• 2 sticks celery, diced
• 1 bay leaf
• 1/2 teaspoon salt
• 1/4 teaspoon white pepper
• 2 tablespoon flour
• 1/4 cup white wine
• 300 millilitre chicken or vegetable stock
• 1 deli roast chicken, deboned and cut into rough chunks
• 1 cup corn kennels - fresh, canned or frozen
• 4 sheets puff pastry
• 1 egg, for the egg wash
• dash milk for the egg wash