Ingredients
Method
1.In a saucepan of boiling, salted water, cook penne according to packet directions. Drain, reserving 1/2 cup of cooking water. Return penne to pan and keep warm.
2.Heat half of oil in a frying pan on medium. Cook leek 5 minutes, stirring, until soft. Add to penne. Heat remaining oil on high and cook mushrooms for 5 minutes, until golden. Add to penne with mascarpone, mozzarella, parmesan, half of blue cheese and reserved water. Stir in spinach. Season.
3.Pour into an ovenproof dish. Top with walnuts and remaining cheese. Place under a hot grill 5 minutes, until golden. Serve.