Heat butter in a nonstick pot or pan over medium-high heat until fully melted.
Add garlic and saute until golden brown. Don't let it burn.
Add flour and mix until combined. It won't be super smooth.
Mix in milk, heavy cream, parmesan cheese, salt, pepper, salt, pepper, ginger powder, Italian seasoning.
Bring the mixture to a boil and then remove from heat.
Mix in half the mozzarella cheese and cheddar cheese. If the cheese mixture is too thick, you can mix in 1/4 cup more milk or heavy cream.
Arrange the sliced sweet potatoes in a large baking dish or casserole dish (Dimensions: 9x13).
Pour the cheese mixture on top.
Sprinkle remaining mozzarella cheese on top.
Cover with foil paper and bake for 30 minutes at 400 degrees F.
Then, remove foil and bake for an additional 5 to 10 minutes until top is golden brown and cheesy mixture is bubbling and sweet potatoes are cooked through and tender.
Garnish with fresh parsley and enjoy!
Note: To make this a one pan side dish, prepare the cheese mixture in a large oven-safe skillet on stovetop and then gently mix in the sliced sweet potatoes. You can also arrange them nicely but you will have to make sure the sweet potatoes are fully covered with the cheese mixture. Sprinkle mozzarella cheese on top. Cover with foil and bake. Then, remove foil and bake. This way, you won't have to make a casserole dish dirty.