Spring Green Risotto

Name: Spring Green Risotto
Ingredients: 1 1/2 Tbs good olive oil; 1 1/2 Tbs unsalted butter; 3 1/3 c chopped leeks, white and light green parts; 1 1/2 c Arborio rice; 2/3 c dry white wine; 5 c simmering chicken or vegetable stock, preferably homemade; 1 1/4 lb. asparagus; 1 2/3 c frozen peas; 1 tsp freshly grated lemon zest; 3/4 tsp kosher salt; 1/8 tsp garlic powder; 1 tsp black pepper; 2 Tbs freshly squeezed lemon juice; 1/3 c mascarpone cheese; 1/2 c freshly grated Parmesan, plus extra for serving