Step 1: Prepare the chicken. If chicken breasts are thick, pound them to an even 1/2-inch thickness. Season both sides generously with salt and black pepper.
Step 2: Cook the chicken. Heat olive oil in a large skillet over medium-high heat. Add chicken breasts and sear for 4-6 minutes per side, until golden brown and cooked through (internal temperature 165°F/74°C). Remove chicken from skillet and set aside.
Step 3: Make the honey garlic butter sauce. In the same skillet, melt 2 tablespoons of butter over medium heat. Add minced garlic and sauté for 1 minute until fragrant. Stir in honey, soy sauce, apple cider vinegar, and red pepper flakes (if using). Bring to a gentle simmer and cook for 2-3 minutes, stirring occasionally, until the sauce slightly thickens.
Step 4: Coat the chicken. Return the cooked chicken to the skillet, turning to coat each piece thoroughly with the honey garlic butter sauce. Keep warm.
Step 5: Cook the macaroni. While the chicken cooks, bring a large pot of salted water to a boil. Add macaroni and cook according to package directions until al dente. Drain and set aside.
Step 6: Prepare the cheese sauce. In a separate large saucepan, melt the remaining 2 tablespoons of butter over medium heat. Whisk in the flour and cook for 1-2 minutes to form a roux. Gradually whisk in the milk until smooth, then bring to a simmer, stirring constantly. Cook until the sauce begins to thicken.
Step 7: Add protein and seasonings. Reduce heat to low. Whisk in the unflavored whey protein powder until fully dissolved and no lumps remain. Stir in Dijon mustard, garlic powder, smoked paprika, salt, and pepper.
Step 8: Incorporate cheese. Gradually add the shredded cheddar and Gruyere/mozzarella cheese to the sauce, stirring constantly until all the cheese is melted and the sauce is smooth and creamy.
Step 9: Combine and serve. Add the drained macaroni to the cheese sauce and stir to combine. Serve immediately with the honey garlic butter chicken, garnished with fresh parsley.