Step 1: Cook the linguine according to package directions in salted water until al dente. Before draining, reserve 1 cup of the starchy pasta water. Drain the linguine and set aside.
Step 2: While the pasta cooks, pat the chicken cubes dry with paper towels. Season generously with salt and pepper.
Step 3: Heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the chicken in a single layer, ensuring not to overcrowd the pan. Sear for 3-4 minutes per side, until golden brown and cooked through. Remove the chicken from the skillet and set aside.
Step 4: Reduce the heat to medium. Add the unsalted butter to the skillet. Once melted, add the minced garlic, chopped parsley, chives, thyme, smoked paprika, and red pepper flakes. Sauté for 1-2 minutes until fragrant, being careful not to burn the garlic.
Step 5: Pour in the chicken broth and lemon juice, scraping up any browned bits from the bottom of the pan. Bring the sauce to a gentle simmer and let it cook for 2-3 minutes, allowing the flavors to meld.
Step 6: Add the cooked linguine and seared chicken back into the skillet with the sauce. Toss well to coat. If the sauce seems too thick, add reserved pasta water a tablespoon at a time until it reaches your desired consistency.
Step 7: Taste and adjust seasoning with salt and pepper as needed. Serve immediately, garnished with fresh Parmesan cheese and an extra sprinkle of fresh parsley, if desired.