Bring a pot of water to a boil, then add the pasta. Cook until al dente according to the package instructions. Rinse the pasta under the faucet to prevent overcooking and clumping.

Place the white mushrooms stem-side down on a cutting board. Cut them into thin slices.

Halve the onion lengthwise, and peel the skin. Trim one end, and lay the halved onion face down. Make vertical slices, 1/8 inch apart, such that you cut towards the root; leave about 1/8 inch at the end so that the root stays intact. Turn the half 90 degrees, and grip the root. Slice the onion horizontally again leaving 1/8 inch at the end to keep the root intact. Chop the onion into small, even cubes. Discard the root.

Remove the root part of each garlic clove. Use the side of a knife to press down and crush the cloves, then peel away the skin. Mince the peeled garlic.

Finely chop the parsley.

Marinate the chicken breasts: In a large mixing bowl, add 20 oz skinless boneless chicken breast, 1/2 tsp pepper, 1/2 tsp paprika, and half the prepared amount of salt. Mix well.

Stir-fry the chicken breast: Place a large non-stick pan over medium heat and add 1 1/2 tbsp olive oil. Gently place the well-seasoned chicken breast in the pan. Pan-sear each side for 2 minutes and 30 seconds, then remove from heat.

Sauté the aromatics: In the same pan, add 1 tbsp unsalted butter, 1 tbsp garlic, and 2 oz diced onion. Sauté until the garlic is fragrant and the onion is translucent for about 1 minute.

Cook the white mushrooms: Continue to add 6 oz sliced white mushrooms. Stir to cook for another 3 minutes.

Add the flour, salt, and garlic powder: To the mushrooms, add 2 tbsp all-purpose flour, 1/2 tsp garlic powder, and the rest of the salt. Stir frequently for 30 seconds.

Add the liquid: Pour 1 cup whole milk, 2 tbsp heavy cream, and 1 tbsp lemon juice into the pan. Stir continuously.

Cut the chicken breasts: Place the stir-fried chicken breasts on a cutting board and cut them into bite-sized chunks.

Combine the chicken and pasta with the sauce: Add 12 oz cooked spaghetti and chicken chunks into the mushroom mixture. Mix well.

Bake the chicken Tetrazzini: Prepare a clean baking dish. Evenly dispense the cooked ingredients into the baking dish. Preheat the oven to 400°F. Place the baking dish in the middle rack of the oven and bake at 400°F for 15 minutes.

Take it out and sprinkle on 1 oz of shredded fresh mozzarella cheese. Return the baking dish to the oven and bake at 480°F for another 5 minutes. Remove from the oven.

Garnish and serve: Transfer your desired portion onto a serving plate. Garnish with 2 tbsp chopped parsley. Enjoy!