This fragrant saffron rice is sunshine on a plate

Ingredients

• 1/3 tsp. loosely packed saffron threads, finely crushed
• 1 tsp. rosewater
• 4 tbsp. olive oil
• 1 large onion, thinly sliced
• 400 g floury potatoes like Maris Pipers (about 2 medium ones), peeled and cut into rough 2.5cm cubes
• 350 g basmati rice, washed until the water runs clear and soaked for at least 20 minutes and up to 2 hours, then drained
• 3 fresh bay leaves
• 5 cloves
• 5 cardamom pods
• 50 g unsalted butter, cut into small cubes
• 4 4 large ripe plum tomatoes, halved lengthways 
• 2 green chillies, left whole
• 1 1/3 tbsp. parsley, roughly chopped (optional)
• Fine sea salt and freshly ground black pepper