1) Bring the stock to the boil in a medium saucepan over high heat. Reduce heat to low and keep at a gentle simmer.
2) Heat a large saucepan over medium heat. Cook the pancetta for 1 min each side or until crisp. Remove and leave aside.
3) Add half of the butter, half the oil and the sliced leek to a large saucepan. Cook, stirring occasionally, for 5 mins or until leek softens. Transfer to a bowl.
4) Add remaining butter, remaining oil, onion and garlic to the pan. Cook, stirring, for 5 mins or until the onion softens. Add the rice. Cook, stirring, for 1 min.
5) Add the wine. Bring to the boil. Cook, stirring constantly, for 2 mins or until absorbed. Add a large ladle of stock and cook, stirring, until the liquid is completely absorbed. Repeat with remaining stock, stirring constantly and allowing the liquid to be absorbed before adding more, until rice is tender yet firm to the bite and the risotto is creamy. This should take about 20 mins.
6) Add the asparagus. Cook for 1 min or until bright green and tender.
7) Coarsely tear the cooked crispy pancetta into pieces. Add to the pan with the leek, lemon zest. Stir to combine.
8) Stir in the grated pecorino (or parmesan). Season with salt & pepper.