Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Reserve about 1/2 cup of pasta water, then drain and set aside.
While the pasta cooks, heat olive oil in a large skillet over medium-high heat. Add the diced chicken breast, season with salt, black pepper, and half the Italian seasoning. Cook until the chicken is golden and cooked through, about 6-8 minutes. Remove the chicken from the skillet and set aside.
In the same skillet, add a little more olive oil if needed, then toss in the broccoli florets and minced garlic. Sauté for 3-4 minutes until the broccoli is bright green and tender-crisp, and the garlic is fragrant.
Lower the heat to medium. Pour in the heavy cream and stir well to combine with the broccoli and garlic. Add the remaining Italian seasoning and the grated Parmesan cheese gradually, stirring continuously until the cheese melts and the sauce thickens slightly.
Return the cooked chicken to the skillet and stir to coat it in the creamy sauce. Add the drained fettuccine pasta and toss everything together. If the sauce seems too thick, add a splash of the reserved pasta water to loosen it up.
Taste and adjust the seasoning with extra salt or pepper if needed. Serve hot, garnished with extra Parmesan or fresh herbs if you like.
