Butter a large casserole dish.

Lay potatoes across the bottom of the casserole dish evenly leaving no holes.

Stack layers until no potatoes remain.

Whisk heavy cream and sour cream together.

Pour cream over potatoes. Press down to even out casserole and distribute cream.

Sprinkle cheese, rosemary, salt, and black pepper across the top.

Spray aluminum foil with non-stick cooking spray and cover casserole dish.

Bake at 400º for 40 minutes. Uncover and cook for approximately 10 minutes or until casserole is bubbly and brown.

Variations; Thyme, herbes de provence, shallots, onion, celery seed, fennel, crispy bacon, oregano, marjoram, mint, basil, parsely, lemon zest, white wine, white vinegar, champagne vinegar, white wine vinegar, peppercorn melange, brown butter, bell peppers, beer, vodka, rum, brandy, garlic, habanero, paprika, smoked paprika, applewood seasoning, asiago, fontina, jalapeños, scallions, chives, leeks, spinach, arugula, swiss, provolone, parmesean, romano, parmigiano reggiano, chervil, fines herbes, caraway, cashews, dijon, carrots, cardamom, espresso, broccoli, roasted bell peppers or garlic, cayenne, crushed pepper flakes, coriander seed, cheddar, blue cheese, gouda, cabbage, goat cheese, chipotle, garlic chives, horseradish, nutmeg, sweet onions, sweet potatoes, parsnips, turnips, butternut squash, acorn squash, yellow squash, capers, tarragon, pesto, dill, asparagus, celery root, turmeric, tomatoes, apple cider vinegar, chicken or vegetable stock, sherry, watercress