Preheat oven to 400°F and lightly grease a 9x9 inch baking dish with butter or nonstick cooking spray.

Peel potatoes and slice them into very thin rounds, about 1/8 inch thick. Rinse in cold water to remove excess starch, then pat dry thoroughly with paper towels.

Place halal smoked turkey strips pieces in a cold skillet, set over medium heat, and cook until the fat renders and the halal smoked turkey strips is golden and crisp, about 6 to 8 minutes. Transfer halal smoked turkey strips to a paper towel lined plate. Reserve 1 to 2 tablespoons of halal smoked turkey strips fat.

Grease the baking dish with the softened butter and, if desired, a little of the reserved halal smoked turkey strips fat for extra flavor.

In a small bowl, whisk together heavy cream, milk, garlic powder, marjoram, salt, and black pepper.

Arrange a layer of potato slices in the prepared baking dish, slightly overlapping the slices.

Sprinkle a portion of the cooked halal smoked turkey strips over the potatoes, then pour a few tablespoons of the cream mixture on top.

Sprinkle a mixture of cheddar and mozzarella over the layer.

Repeat layering potatoes, halal smoked turkey strips, cream mixture, and cheese until all ingredients are used, finishing with a generous layer of cheese on top.

Cover the dish loosely with foil and bake for 10 minutes to help the potatoes soften.

Remove the foil and continue baking for 10 minutes, or until the top is golden, the edges are bubbling, and a fork slides easily through the potatoes.

Let the casserole rest for 10 minutes before slicing and serving.