1Melt oil and butter together in a large heavy bottomed saucepan over medium heat. Stir in chopped leeks, onion, and celery. saute gently for about 15 minutes to allow leeks and onions to sweat and become translucent, but not brown.
2Add rice and garlic and mix well, coating rice in oil. Cook, stirring often, for a couple of minutes to allow rice to heat through, but not brown. Now stir in herbs and white wine (if using).
3Add a couple of ladlefuls of hot stock (about 1/4 cup), enough to cover rice. Stir well and simmer gently, stirring frequently until stock is nearly absorbed. Do not let rice cook too quickly.
4Gradually add more stock and keep stirring until all of it has been absorbed; do not allow risotto to dry out. You want a thick, soupy consistency. Stir in peas halfway through cooking the rice, after about 7 minutes.
5After about 15 minutes rice should be cooked through but still al dente. If you run out of stock and rice is not cooked yet, use some extra stock or hot water to finish it off- but be careful not to let it overcook and become soggy or sticky.
6Season with black pepper. Taste rice and add salt, if needed. Remove from heat and stir in Parmesan cheese. Mix well and let stand for 1 or 2 minutes. Then serve immediately with extra Parmesan cheese and black pepper sprinkled over the top.