Step 1: Cook the linguine: Bring a large pot of salted water to a rolling boil. Add 12 ounces of linguine and cook according to package instructions until al dente—usually about 8 to 10 minutes. Drain well, reserving a cup of pasta water in case you need to loosen the sauce later, then set the linguine aside.
Step 2: Season and sear the chicken: While the pasta cooks, pat 1½ pounds of chicken breast or thigh strips dry and season generously with salt and pepper. Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add the chicken in a single layer and cook, without stirring, for 3 to 4 minutes to develop a golden crust. Flip and cook another 2 to 3 minutes until fully cooked through. Transfer the chicken to a plate and cover loosely with foil to keep warm.
Step 3: Melt butter and infuse with garlic: In the same skillet, reduce heat to medium and add 6 tablespoons of unsalted butter. Once the butter has melted, stir in 4 cloves of minced garlic. Cook, stirring constantly, for about 1 minute—just until the garlic is fragrant and the butter begins to bubble. Be careful not to let the garlic brown, as this can introduce a bitter edge.
Step 4: Build the cowboy butter sauce: Reduce heat to medium-low. To the melted garlic butter, add 1 teaspoon smoked paprika, ½ teaspoon crushed red-pepper flakes (if using), 1 tablespoon Dijon mustard, and the juice of ½ lemon. Sprinkle in ½ teaspoon dried thyme, ½ teaspoon dried rosemary, and 1 tablespoon chopped parsley. Stir continuously for 1–2 minutes, allowing the spices to bloom and the mustard to emulsify the sauce.
Step 5: Reincorporate the chicken: Return the seared chicken strips to the skillet. Toss to coat each piece in the sauce, then let them warm through for 1–2 minutes so the meat reabsorbs those smoky, herbed butter notes.
Step 6: Combine pasta and sauce: Add the cooked linguine directly into the skillet. If the pan is tight, use tongs to gently lift and fold the pasta into the sauce. Pour in up to ¼ cup of reserved pasta water—just enough to help the sauce adhere and achieve a silky consistency.
Step 7: Finish with Parmesan: Sprinkle ½ cup grated Parmesan cheese over the pasta and chicken. Toss until the cheese melts into the sauce, creating a creamy coating on every strand of linguine. Taste and adjust seasoning with salt, pepper, or another squeeze of lemon if needed.
Step 8: Serve and garnish: Transfer the linguine and chicken to warmed plates or a large serving bowl. Garnish with extra chopped parsley and lemon wedges on the side. Serve immediately, inviting guests to squeeze fresh lemon or add a dash of hot sauce to taste.