Preheat oven to 375°F (190°C).
Cut chicken breasts into bite-sized pieces.
Heat olive oil in a large skillet over medium-high heat.
Add chicken and cook until browned on all sides and cooked through (about 6-8 minutes), reaching an internal temperature of 165°F (74°C).
Remove chicken from skillet and set aside.
In the same skillet, sauté chopped onion until softened (3-5 minutes).
Add minced garlic and cook for 1 minute more.
Stir in cream of mushroom soup, cream of chicken soup, milk, Parmesan cheese, parsley, pepper, and salt.
Bring to a simmer, stirring occasionally, until slightly thickened (5-7 minutes).
Stir in heavy cream and mozzarella cheese until melted and smooth.
Remove from heat.
Lightly grease a 9×13 inch baking dish.
Pour half the Alfredo sauce into the dish.
Add the cooked chicken, then top with the remaining sauce.
Arrange cooked tater tots in a single layer.
Sprinkle with cheddar cheese (optional).
Bake for 20-25 minutes, or until tater tots are golden brown and cheese is melted and bubbly.
Let rest for 10 minutes before serving.