Set milk out to reach room temperature. In a small bowl, stir together garlic powder, onion powder, mustard powder, pepper, and salt. Set aside.
Heat olive oil in a large nonstick pot over medium heat. Add shallots, season lightly with salt and pepper (I add 1/4 tsp each), and cook, stirring often, until lightly golden, about 3-5 minutes. Add asparagus and cook 2-3 minutes until bright green. Stir in peas and garlic and cook 1 minute. Transfer everything to a bowl and cover with foil to keep warm.
Keep heat at medium and add 3 tablespoons butter to the empty pot. Once melted, stir in the seasoning mixture and cook, stirring constantly, until the butter foams.
Pour in chicken broth and milk and stir. Bring to a boil, add pasta shells, then reduce to a gentle boil and cook uncovered for 7-10 minutes, stirring often, until pasta is tender and most of the liquid is absorbed, leaving a creamy sauce. Scrape the bottom of the pot with a silicone spatula often as it cooks to prevent sticking.
Remove from heat. Stir in Parmesan one handful at a time until melted and smooth. Add cooked veggies, remaining 1 tablespoon butter, lemon zest, and lemon juice. Gently stir to combine. If needed, add a splash of milk to thin the sauce. Taste and adjust seasoning as needed.
Serve immediately with extra Parmesan and parsley if desired.
Notes
Note 1: Prepare asparagus by washing and removing the tough, woody ends, either snap each spear at its natural break point or cut off the bottom 1 to 2 inches. Cut on a diagonal into 1-inch pieces and make sure it’s fully dry before adding to the pot.Note 2: VERY important! Use a block of Parmesan and grate it very finely with a microplane. It takes a little extra time but makes a big difference in flavor and texture. Gently pack into measuring cups for the correct amount.Storage: Asparagus Pasta Recipe is best enjoyed right off the stovetop while the sauce is smooth and creamy. Store leftovers in an airtight container in the fridge for up to 3 days. Reheat gently with a splash of milk to loosen the sauce.