Heat the olive oil in a large cast iron pan over medium heat. Add the leeks, garlic and arborio rice. Sauté until the leeks are soft and the edges of the rice become translucent. Add the salt and the white wine or vinegar and scrape up the pan. Allow the liquid to reduce.
Begin adding the stock: Add one cup at a time, once the liquid has reduced almost completely add the next cup. Mix the rice constantly and avoid it from sticking to the bottom.
After adding the sixth cup, allow the liquid to boil and taste the rice. It should be soft all around the edges and have a little bit of a bite in the center. If it needs to cook longer, add the seventh cup. Otherwise, add the cheese, lemon zest, cream and freshly cracked pepper. Mix vigorously to create an emulsion between the fats and liquids. Add extra salt if you need to. You should end up with a lot of creamy sauce and rice al dente.
In a hot pan, melt the butter and brown the pears, about a minute per side.
Immediately serve the risotto and top with the pears. Drizzle extra lemon zest and pepper.