Chicken and Spring Vegetable Pot Pie

Ingredients

• 500 g washed potatoes, cut into bite sized pieces
• 3 carrots, peeled and cut into rounds
• 3 tbsp olive oil, divided
• 400 g chicken thighs, cut into bite sized pieces
• 1 leek, thinly sliced
• 4 cloves garlic, finely chopped
• 1 fennel bulb, thinly sliced
• ¼ cup plain flour
• 2 cups milk
• 2 tsp Dijon mustard
• ½ tsp table salt
• ½ tsp freshly ground black pepper
• 1 bunch asparagus, woody ends removed, cut into pieces
• 1 cup fresh or frozen peas
• 2 tbsp lemon juice
• ½ cup water
• 1 tbsp thyme, chopped
• 1 tbsp tarragon, chopped
• 2 tbsp chives, finely chopped
• 1 sheet puff pastry
• 1 egg, lightly whisked
• 1 lemon, cut into wedges, to serve