01 -
Preheat oven to 190°C and position a rack in the center. Thoroughly butter a 2-liter shallow oval baking dish or medium ovenproof skillet and set aside.
02 -
In a small saucepan over medium-low heat, combine shallots, garlic, cream, and thyme. Heat to a gentle simmer and cook, stirring occasionally, until shallots and garlic are very tender, approximately 15 minutes. Remove from heat, discard thyme, and cool slightly.
03 -
Transfer contents to a blender or use an immersion blender to puree until smooth, creating a creamy sauce.
04 -
Spread one-third of the cream sauce evenly over the bottom of the prepared dish. Layer half of the potato slices over the sauce, lightly seasoning with salt and pepper. Add half of the ham slices, followed by another third of the cream sauce. Repeat layers with remaining potatoes, ham, and sauce, ending with the final third of sauce. Cover the dish tightly with foil.
05 -
Bake covered for about 60 minutes, or until the sauce is bubbling and potatoes are tender when pierced.
06 -
Remove foil and evenly sprinkle Gruyère and Parmesan cheeses over the top of the casserole.
07 -
Switch oven to broil. Broil the casserole closely watching for approximately 4 minutes, or until the cheese is melted, bubbly, and golden brown without burning.
08 -
Remove from oven, garnish with freshly chopped parsley, and serve immediately.