• Add butter to a sauce pan over medium heat. Once melted add onion and a pinch of salt and cook for a few minutes until starting to tenderize and become transluscent. Add garlic and thyme cook for one more minute or until fragrant but not browned.
• Whisk in the flour and cook for a few minutes to create a roux.
• Once the flour taste has cooked out, whisk in the milk and let the sauce simmer and thicken. Slowly stir in half the cheese (little by little) until the sauce is smooth and creamy.
• Grease your crockpot and add ½ cup of the cheese sauce to the bottom followed by half of the potatoes, a generous sprinkle of salt, and half of the shredded cheese.
• Now add the rest of the potatoes, another generous sprinkle of salt, the rest of the cheese sauce and the other pile of cheese.
• Place the lid on and cook for 3-4 hours on high.

For the Topping

• Once the potatoes are tender to the touch, take the lid off the crockpot (while it's still cooking on high heat) and make the crispy toppings.
• Heat a small fry pan over medium and melt butter and dried rosemary together until bubbling and fragrant.
• Add bread crumbs and continuously move them around until they're golden brown and toasty. Remove from heat and sprinkle over potatoes before serving.