40g unsalted butter
1 leek (white part only), thinly sliced
6 button mushrooms, sliced
2 tbsp plain flour
3/4 cup chicken stock
3/4 cup thickened cream
2 tbsp good-quality basil pesto, plus extra to serve if desired
3 cups chopped cooked chicken
6 large, ready-made vol-au-vent cases
2 sheets frozen puff pastry, thawed
1 egg, lightly beaten
1 tsp nigella seeds or sesame seeds (optional)
250g cherry tomatoes
1 tbsp olive oil
Preheat the oven to 180C. Melt butter in a pan over medium-low heat. Add leek and cook, stirring, for 5 minutes or until soft. Add mushroom and cook for a further minute, then add flour and stir for 1 minute. Gradually stir in chicken stock, then bring mixture to simmer. Add cream and cook for 2-3 minutes, stirring, until thickened. Cool, season, then stir in pesto. Stir the chicken into the sauce.
Using a vol-au-vent as a template, cut 6 lids from puff pastry sheets. Place vol-au-ents on a baking tray and fill with chicken mixture. Brush edge of pastry lids with a little water and place on top, pressing edges to seal. Brush tops of pies with beaten egg and sprinkle with nigella seeds, if using. Bake for 15-20 minutes until golden.
Meanwhile, place tomatoes on a tray, drizzle with olive oil and season. Bake in the oven with pies for 6-8 minutes until tomatoes are just starting to burst. Serve pies with tomatoes and extra pesto, if desired.