Start by shredding or dicing your cooked chicken, which should yield about three cups. If you prefer using raw chicken, heat a tablespoon of olive oil in a skillet over medium heat. Cook the chicken for 6-8 minutes, or until fully cooked and tender. Once ready, remove from heat and shred the meat.

In the same skillet, add a tablespoon of butter over medium heat. Once melted, toss in the finely chopped onion and sauté for about 2-3 minutes until fragrant and translucent. Add in minced garlic and continue cooking for another minute, stirring frequently.

After the aromatics are ready, add 4 tablespoons of butter to the pan and let it melt. Gradually pour in 1 cup of heavy cream, whisking continuously to combine. Next, gradually mix in 1 cup of grated Parmesan cheese, whisking until smooth. Season with Italian seasoning, salt, and pepper to taste, and let simmer for about 5 minutes.

Gently fold the shredded chicken into the creamy Alfredo sauce, ensuring every piece is well coated. If adding optional ingredients like chopped spinach or roasted red peppers, incorporate them now. Allow it to heat together on low for 3-4 minutes.

Prepare your sandwich buns by lightly toasting them. Spoon generous portions of the chicken Alfredo mixture onto the bottom halves of the toasted buns. If desired, top with additional shredded mozzarella. Place the top buns on and serve immediately.