Step 1: Cook fettuccine according to package directions in a large pot of heavily salted water until al dente. Reserve 1 cup of pasta water before draining. Set aside.
Step 2: While pasta cooks, pat chicken breasts dry and season generously with garlic powder, salt, and black pepper.
Step 3: Heat olive oil in a large skillet or pan over medium-high heat. Add chicken and cook for 5-7 minutes, turning occasionally, until golden brown and cooked through. Remove chicken from pan and set aside.
Step 4: Reduce heat to medium. Add butter to the same skillet. Once melted, add minced garlic and cook for 1 minute until fragrant, being careful not to burn.
Step 5: Slowly pour in the heavy cream, whisking continuously. Bring to a gentle simmer, then reduce heat to low and whisk gently for 5-7 minutes until slightly thickened.
Step 6: Gradually add the grated Parmigiano-Reggiano cheese, a handful at a time, whisking constantly until completely melted and smooth. Continue to whisk over low heat until the sauce is creamy. Taste and adjust seasoning with salt and pepper.
Step 7: Add the drained fettuccine and cooked chicken back into the skillet with the Alfredo sauce. Toss gently to coat everything evenly. If the sauce is too thick, add a tablespoon or two of the reserved pasta water until desired consistency is reached.
Step 8: Serve immediately, garnished with fresh chopped parsley and extra grated Parmesan cheese.