In a large pot on a medium – high heat, melt half of the butter. Once bubbling and melted, drizzle over olive oil. Bring to the heat. Add the white and pale green parts of the leek to pan, reserving the leek tops, shallots and garlic and sauté for 10 minute or until softened and fragrant. Stir occasionally.
Add the rice to the pot and cook for 2 minutes or until the rice turns opaque. Add in the wine and keep stirring with the rice until all of the wine has been absorbed by the rice.
Reduce the heat to medium. One cup at a time, add in the chicken or vegetable stock and stir through until all the stock is absorbed. Repeat this step 5 more times until you have used up all of your stock. Your rice will start to become plump as it continues to cook and absorb the stock. It should take roughly 25 minutes to cook. When you have added your last cup of stock you want only 80% of the liquid to be absorbed.
Turn the heat to low and stir through the remaining butter, parmesan cheese, lemon zest and juice and pinch of salt and pepper.
Quickly fry off the leek tops in a separate fry pan on a high heat with a drizzle of olive oil for 2 minutes or until crispy. Sprinkle over the risotto and serve immediately.