Lemon risotto with crisp sage

Name: Lemon risotto with crisp sage
Ingredients: 1 ¼ litres light chicken stock; 60g unsalted butter; 4 sticks celery, finely chopped; 1 fennel bulb, finely chopped; 1 unwaxed, organic lemon; 300g risotto rice; 100ml Martini Bianco (or other sweet white vermouth); 2 tablespoons olive oil; 30g sage leaves; 20g grated Parmesan