Preheat the oven to 200C. Drizzle oil over a large casserole dish and place in the oven to heat up. Add the leek, mushrooms and chicken drumsticks to the pan and return to the oven for 20mins.
Sprinkle Risoni and peas around the chicken and then pour over the cream, chicken stock, lemon and lemon zest. Lay the lemon slices on top. Return to the oven for 25mins.
Top with freshly grated parmesan cheese.