Tava lamb with avocado and radish salad

Name: Tava lamb with avocado and radish salad
Prep time: 30 min
Cook time: 2 h
Total time: 2 h 30 min
Cuisine: European, Greek, Mediterranean
Ingredients: 4 onions, cut into thin wedges; 800g/1lb 12oz Cypriot or other potatoes, peeled and cut into 4cm/1½in chunks; 900g/2lb lamb neck fillet, cut into 4cm/1½in chunks; 80ml/2½fl oz olive oil; 1 tbsp ground cumin; 3 bay leaves; 2 tbsp tomato purée; 6 ripe tomatoes, roughly chopped; 75g/2¾oz long-grain rice; 350ml/12fl oz hot chicken stock; ½ bunch fresh flatleaf parsley, finely chopped; sea salt and freshly ground black pepper; 1 garlic clove, bruised; 1 lemon, juice only; 3 tbsp extra virgin olive oil; 1 heaped tbsp tahini; 2 tbsp sesame seeds, toasted; 4 spring onions, trimmed and finely sliced; ½ bunch fresh mint, leaves picked and chopped, plus extra to garnish; 250g/9oz radishes, some sliced and some roughly chopped; 2 Little Gem lettuces or 1 romaine lettuce, trimmed, washed and large leaves chopped; 2 avocados, stones removed and flesh chopped