Heat a large skillet over medium heat and add a drizzle of olive oil.
Add the minced leek and sauté until softened, about 3–4 minutes. Stir in the garlic and cook for another 30 seconds until fragrant.
Add the orzo and pour in the stock. Cover and cook for 5 minutes, stirring occasionally.
Stir in the chopped asparagus, cover again, and cook for another 2 minutes. Then, add the frozen peas and stir to combine.
Add the grated lemon zest and the juice of half the lemon. Cook for another minute until the peas are heated through.
Remove from heat and stir in the butter and a generous amount of shaved Parmesan.
Serve immediately with extra Parmesan, freshly ground black pepper, and a squeeze of lemon juice.