Easy sausage fennel risotto

Name: Easy sausage & fennel risotto
Ingredients: 2 tbsp olive oil; 1 onion, finely chopped; 1 fennel bulb, finely sliced; 2 pork sausages; ½ tsp fennel seeds, crushed (optional); 2 large garlic cloves, crushed; 3 thyme sprigs, leaves finely chopped, plus extra to serve; 400g risotto rice; 100ml white wine; 1.4 litres hot chicken stock; 70g parmesan, finely grated; 1 lemon, zested and juiced