Chicken in a pot with lemon and orzo

Name: Chicken in a pot with lemon and orzo
Ingredients: 1 whole chicken, approx. 1.5kg/3lb 5oz; 1 tbsp olive oil; 2 lemons, zest and juice; 3 fat garlic cloves, grated; 2 tsp dried tarragon (or dried thyme); 2 medium carrots, peeled and cut into batons; 2 medium leeks, cut into 2cm/¾in rounds; 2 tsp sea salt flakes (or 1 tsp fine sea salt); ½ tsp dried chilli flakes (optional); 300g/10½oz orzo; 6 tbsp finely chopped flat-leaf parsley, plus extra to serve; freshly grated Parmesan, to serve (optional)