Preheat your oven to 200°C (400°F).

Peel and slice the potatoes into thin rounds. Set aside.

In a large skillet over medium heat, cook the bacon until crisp. Remove the bacon and set aside, leaving the fat in the skillet.

Add the garlic and spring onions to the skillet and sauté for 1-2 minutes until fragrant and softened.

In the same skillet, melt the butter over medium heat. Stir in the flour and cook for about 1 minute to form a roux.

Gradually whisk in the chicken stock, milk, and cream, stirring continuously until the mixture is smooth and starts to thicken.

Add the thyme, salt, and pepper. Allow the sauce to simmer gently for a few minutes to develop the flavors.

Remove from heat and stir in half of the grated cheddar until melted and smooth.

In a large baking dish, layer half of the sliced potatoes. Pour half of the cheese sauce over the potatoes, then sprinkle with half of the cooked bacon.

Repeat the layers with the remaining potatoes, cheese sauce, and bacon.

Top with the remaining grated cheddar cheese.

Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.

Remove the foil and continue to bake for another 30 minutes or until the top is golden brown and bubbly, and the potatoes are tender.

Let the potato bake rest for a few minutes before serving to allow the layers to set.