1. Preheat your oven to 375°F (190°C) and butter a 9×13-inch baking dish generously.
2. In a medium saucepan over medium heat, melt the butter and sauté the minced garlic until fragrant, about 1 minute.
3. Add the heavy cream, milk, salt, and pepper to the saucepan, stirring to combine. Bring the mixture to a gentle simmer.
4. Reduce the heat to low and slowly stir in the cheddar cheese and Parmesan, allowing them to melt completely into the cream mixture.
5. Layer half of the sliced potatoes evenly in the prepared baking dish. Pour half of the cheese sauce over the potatoes, spreading it evenly.
6. Repeat with the remaining potatoes and cheese sauce, ensuring the top layer is fully covered with sauce.
7. Sprinkle the fresh thyme leaves over the top, if using, and dust with paprika for a touch of color and flavor.
8. Cover the dish with aluminum foil and bake in the preheated oven for 45 minutes.
9. Remove the foil and bake for an additional 15 minutes, or until the top is golden and the potatoes are tender when pierced with a fork.
10. Let the dish cool for a few minutes before serving, allowing the flavors to meld beautifully.

From my mum’s teaching, I learned the importance of patience—let the potatoes sit for a bit before serving, so the cheesy sauce thickens and clings to the potatoes perfectly.