Cook pasta in a large pot of salted water according to package directions. Drain and place in a large pot with the butter. Use tongs to coat the pasta with the butter as it melts. Set aside.: As the pot of water comes to a lively boil you will smell a faint mineral sweetness, and the salted water seasons the pasta from the inside. Once the Angel Hair pasta is al dente, drain quickly so it does not continue to soften; the strands should still have a slight tooth when you bite them. Transferring the hot pasta into a warm pot and adding cold pieces of butter creates a sheen that prevents clumping and helps the sauce adhere. Use tongs to gently toss, feeling the glossy, slick surface as the butter melts and coats every strand. If the pasta feels sticky, you likely left it sitting too long after draining, so toss immediately. A common mistake is rinsing the pasta which washes away seasoning and starches needed to bind the sauce.
Heat olive oil in a large nonstick skillet. Add shrimp and asparagus and cook for 2 minutes. Add garlic and continue to cook until shrimp are opaque. Add red pepper flakes and season with salt and pepper. Set aside.: When the skillet is hot and the olive oil shimmers, add the shrimp and asparagus and listen for a soft sizzle that signals immediate contact. After about two minutes the edges of the asparagus will bright en and the shrimp will begin to curl; their flesh will transition from translucent to an opaque pink. Adding minced garlic briefly releases a fragrant hit of allium without browning, which keeps it sweet rather than bitter. Sprinkle the crushed red pepper flakes now so their heat infuses the oil and blossoms across the pan. Season to taste with salt and pepper , then remove the mixture to avoid overcooking the shrimp . Watch for a rubbery texture, a sign of overcook, especially with large shrimp types.
Whisk together heavy cream and egg yolks in a medium saucepan. Heat over medium heat just until really warm, do NOT let it boil. Then stir in lemon juice and zest and Parmesan cheese. Remove from heat. Season to taste with salt and pepper.: As you whisk the heavy cream and egg yolks , notice the gloss forming, a promise of silkiness. Warm the mixture gently so it becomes cozy to the touch but does not bubble, because boiling will curdle the eggs and break the sauce. Once warm, the bright perfume of freshly zested lemon and the sharp, nutty aroma of melting Parmesan cheese will bloom, transforming the cream into a lemon kissed emulsion. Remove from heat promptly when the cheese has melted into a smooth consistency, then taste and adjust with salt and pepper . If the sauce begins to look grainy, it may have overheated; cool slightly and whisk vigorously to bring it back together.
Pour lemon sauce over pasta and mix in. Add shrimp/asparagus mixture. Sprinkle parsley on top and serve.: When you pour the warm lemon cream over the glossy pasta , it should cling immediately, coating each strand in a luminous veil. Toss gently with tongs so the sauce threads through the noodles and creates a cohesive dish. Fold in the cooked shrimp and asparagus , noticing the contrast of colors and textures: pale pasta, pink shrimp , and vibrant green. Finish with a scattering of chopped parsley , which adds a fresh, herbal lift and visual brightness. Serve right away while steam rises and aromas of citrus and cheese mingle. If left too long, the pasta will soak up the sauce and dry out, so plate promptly.