Begin by bringing a large pot of salted water to a vigorous boil. Add spaghetti and cook according to package instructions until al dente, typically around 8-10 minutes. Once cooked, drain the pasta in a colander, reserving a tablespoon of the pasta water for later use. Set the drained spaghetti aside.

In a large skillet, heat butter over medium-high heat until melted. Add minced garlic and sauté for about 1-2 minutes until fragrant and lightly golden. Incorporate the zest and juice of lemon along with white wine. Bring the mixture to a gentle simmer for about 5 minutes until slightly reduced.

Gradually whisk in flour into the simmering sauce, stirring continuously until it is smooth and begins to thicken, which should take about 2 minutes. Slowly pour in heavy cream, followed by Italian seasoning. Continue to simmer the sauce for another 5 minutes.

Carefully add peeled and thawed shrimp to the skillet. Stir and cook for about 5 minutes, or until the shrimp turn pink and opaque.

Toss the cooked spaghetti into the creamy lemon shrimp sauce, adding the reserved tablespoon of pasta water. Mix well until the spaghetti is fully coated. Serve immediately, garnished with freshly chopped parsley.