Begin by bringing a large pot of salted water to a rolling boil. Once boiling, add your spaghetti or angel hair pasta, cooking according to package instructions until it reaches al dente, typically about 8-10 minutes. Remember to reserve ½ cup of the starchy pasta water before draining the pasta in a colander.

While the pasta is cooking, pat the peeled and deveined shrimp dry with a paper towel. Season the shrimp with salt and pepper. Heat a large skillet over medium-high heat with olive oil, then add the shrimp in a single layer. Sear for approximately 30 seconds on each side until they're pink and opaque. Remove from the skillet and set aside.

In the same skillet used for the shrimp, reduce the heat to medium and add a tablespoon of butter along with the shallots. Sauté for 1-2 minutes until the shallots become translucent, then add minced garlic, cooking for another minute until fragrant. Toss in fresh basil and crushed red pepper flakes, continuing to sauté for an additional 2 minutes.

Pour in the vegetable stock, followed by the fresh lemon juice and zest. Allow the mixture to simmer, reducing it by half, which should take about 3-5 minutes. Stir in the remaining tablespoon of butter, then add the cooked shrimp, crab meat, and the reserved pasta water. Toss in the drained pasta, mixing everything together until well-combined.

Increase the heat slightly and cook the combined mixture for an additional 2 minutes. Taste and adjust seasoning with salt and black pepper as needed. Serve immediately, garnished with chopped parsley and a sprinkle of Parmesan cheese if desired.