Roast the garlic

• Preheat the oven to 200 °C (400 °F).
• Slice the top off the garlic heads, drizzle with olive oil and season with salt and pepper.
• Wrap in foil and roast until soft and caramelized.
• Let cool, squeeze the roasted garlic from the cloves and mash with a fork. Set aside.

Prepare the potatoes

• Wash and peel the potatoes.
• Slice them thinly, about 1/8-inch thick.
• Place the sliced potatoes in a bowl of cold water to prevent browning.

Infuse the cream

• In a saucepan over medium-low heat, warm the half & half with the fresh thyme, rosemary, bay leaf, Parmesan rind and salt.
• Simmer gently, then strain and set aside.

Cook the onions

• In a saucepan over medium heat, add olive oil, butter and the onions.
• Cook until translucent.

Make the sauce

• Add the flour and whisk until the flour is cooked.
• Pour in the infused half & half, stirring to combine, and simmer until thickened, stirring frequently.
• Add the garlic powder, onion powder, dried thyme, smoked paprika and roasted garlic, and mix until combined.
• Stir in the cheeses until melted and smooth, then season with salt and pepper to taste.

Assemble the dish

• Grease a 9x13-inch baking dish with butter or cooking spray.
• Layer the sliced potatoes evenly in the dish, slightly overlapping.
• Pour the creamy sauce over the potatoes and spread so they are evenly coated.

Bake covered

• Cover the dish tightly with aluminum foil.
• Bake until the potatoes are tender when pierced with a fork.

Brown the top

• Remove the foil and bake uncovered on broil until the top is golden and bubbly.