Easy Potato Gratin

Potatoes and cast iron cookware are old friends. Most opt for crispy roasted potatoes. This recipe is not about that. This recipe is about making the richest most decadent potatoes you've ever had. The idea is simple: potatoes, cream, and cheese plus savory flavors. The result is more than the sum of its parts.

Ingredients

3 to 3½ pounds russet potatoes, peeled and sliced ⅛ inch thick on a mandoline slicer (about 4 medium potatoes)
1 tablespoon unsalted butter, room temperature
2½ cups heavy cream
3 garlic cloves, minced
1 tablespoon fresh thyme leaves, roughly chopped
Kosher salt and freshly ground black pepper
3 ounces Gruyère, finely grated
1 ounce Parmesan cheese, finely grated
1 tablespoon diced chives for garnish