Marrakech lamb with tahini squash gratin

• 1.6-1.8 kg boned shoulder of lamb (ask the butcher to do this for you)
• 2 tablespoon olive or rapeseed oil
• 1 red onion, chopped
• 3 garlic cloves, crushed
• 2 tsp ground coriander
• 2 tsp ground cumin
• 1 tsp ground cinnamon
• 1 tsp sumac
• 50 g fresh breadcrumbs
• little lot parsley, chopped
• little lot mint, sliced, plus a couple of entire mint leaves to serve
• 85 g pistachios, approximately chopped
• 100 g feta, crumbled
• 60 g pack dried sour cherries
• 2 small maintained lemons, rind only, carefully chopped
• 3 tablespoon tahini
• Saffron yogurt, to serve (see suggestion for dish)

For the gratin

• 1 large butternut squash, or 2-3 smaller sized seasonal squashes like acorn or onion
• 4 tbsp tahini
• 100 ml double cream
• 300 ml chicken or lamb stock