Bring a large pot of heavily salted water to a boil. Add the linguine and cook according to package directions until al dente. Before draining, reserve about 1 cup of the starchy pasta water.

While the pasta cooks, pat the chicken breast cubes dry with a paper towel. In a medium bowl, toss the chicken with smoked paprika, salt, and pepper until evenly coated.

Heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the seasoned chicken in a single layer (work in batches if necessary to avoid crowding). Cook for 3-4 minutes per side, until golden brown and cooked through. Remove the chicken from the skillet and set aside on a plate.

Reduce the heat to medium. Add the butter to the same skillet. Once melted, add the chopped shallot and cook for 2 minutes until softened. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Stir in the parsley, chives, thyme, Dijon mustard, red pepper flakes, and lemon zest. Cook for 30 seconds, stirring constantly, to bloom the flavors.

Pour in the chicken broth to deglaze the pan, scraping up any browned bits from the bottom of the skillet with a whisk or wooden spoon. Let it simmer for 1-2 minutes to reduce slightly.

Reduce heat to low and slowly whisk in the heavy cream until combined. Bring to a gentle simmer, then stir in the grated Parmesan cheese until the sauce is smooth and creamy. Do not let it boil after adding the cheese.

Return the cooked chicken and any accumulated juices to the skillet. Add the drained linguine. Toss everything together to coat the pasta and chicken thoroughly in the sauce. If the sauce is too thick, add a splash of the reserved pasta water until it reaches your desired consistency.

Stir in the lemon juice and taste for seasoning, adding more salt and pepper if needed. Serve immediately, garnished with extra fresh parsley and a pinch of red pepper flakes.