Preheat the oven to 375°F. Spray a casserole dish with nonstick spray, & sprinkle with just a bit of shallot.

In a medium saucepan, add the heavy cream, the remaining shallot, garlic, salt & pepper, to taste. Cook over medium heat & bring to a simmer while stirring. Let simmer for about 2 to 3 minutes.

Later 1/3 of the sliced potatoes in the casserole dish, cover with some cheddar cheese, & sprinkle the Parmesan cheese. Repeat layering 2 more times. Pour the heavy cream mixture over the potatoes. Add the remaining cheese.

Cover with a foil. Bake for 1 hour. Then remove the foil to bake until the cheese is golden & brown, about 15 to 20 minutes.

Take out of the oven & let it rest for 10 minutes before slicing & serving.