Melt 2 tablespoons butter in a medium saucepan over medium heat. Stir in garlic and cook until fragrant, about 30 seconds. Add chicken stock and bring to a boil.
Stir in orzo, ¼ teaspoon salt, ½ tsp pepper and return to a gentle simmer. Cook uncovered, stirring once, for 8 minutes.
Stir in asparagus and simmer for another 2 minutes, until orzo is al dente and asparagus is crisp-tender, adding a splash more stock if needed.
Remove from heat and add remaining 2 tablespoons butter, lemon zest, lemon juice and parmesan, stirring until butter is melted and a thin sauce coats the pasta. Season to taste with more salt and pepper. Stir in parsley and serve.
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