Preheat your oven to 375°F (190°C).
Prepare a baking dish with some butter or non-stick spray.
In a mixing bowl, combine the heavy cream, milk, minced garlic, salt, and pepper.
Layer half of the sliced potatoes in the bottom of the baking dish.
Spread half of the Boursin cheese over the first layer of potatoes, followed by half of the cream mixture.
Repeat the layers with the remaining potatoes, Boursin cheese, and cream mixture.
Top the final layer with grated Gruyère cheese and fresh parsley.
Cover the baking dish with aluminum foil and bake for 45 minutes.
Remove the foil and continue baking for an additional 15-20 minutes until golden brown.
Allow the dish to cool for 10 minutes before serving.