Snap off tough ends of asparagus; chop ends into 1-inch/2.5 cm pieces. Tie string around spears to make bundle.

In large saucepan, bring stock, 1-1/2 cups/375 mL water and asparagus ends to boil; add asparagus bundle and cook until spears are tender, 4 to 6 minutes.

Remove bundle; chill under cold water and drain. Cut spears into 2-inch/5 cm lengths; set aside. Meanwhile, bring stock (with asparagus ends) to gentle simmer; maintain over low heat.

In saucepan, heat oil and butter over medium heat; fry onion until softened, about 5 minutes. Add rice and lemon rind; fry, stirring, until rice has absorbed oil and grains are translucent with white centres, about 3 minutes. Add 1 cup/250 mL of the stock (liquid only); cook, stirring constantly, until liquid is absorbed.

Continue adding stock (liquid only), 1 cup/250 mL at a time, stirring rice almost constantly, until creamy and tender yet slightly resilient, about 18 minutes in total, and adding chopped asparagus spears about 2 minutes before rice is fully cooked.

Stir in lemon juice; stir in cheese. Add salt to taste. Stir in 1/4 cup/60 mL of the stock (liquid only). Serve immediately.

Makes 4 main-course dinner servings, or 6 first-course or lunch servings.