Preheat oven to 200°C fan
Add cauliflower and leeks to a large roasting dish with olive oil, salt, pepper, garlic powder and turmeric, mix well
Roast for 50 minutes, turning halfway through, and reduce temperature to 170°C for the last 15 minutes
Heat oil in a frying pan on high heat, add chillies and char for 2 minutes on each side until blistered and blackened
Remove chillies from pan and finely chop
Mix 2 tbsp butter with 1 heaped tsp white miso paste and add to cooked cauliflower along with chopped chillies, mix well and set aside to cool completely
Turn oven up to 220°C and place a tray inside to heat up
Roll out pastry and cut into 4 rectangular quarters
Spread 2 tbsp Boursin on the base of one pastry piece, add generous amount of cauliflower mixture leaving a small border, top with 30g grated cheddar
Add another pastry piece on top, press down and seal with a fork, repeat with remaining pastry pieces
Chill or freeze pastry until ready to bake
Brush with beaten egg, place on hot tray in oven and bake for 30 minutes until pastry is puffed up and golden
