Preheat the oven to 190°C. 

1. Grease a baking dish with butter or cooking spray and set aside.
2. Wash and peel the potatoes, then slice them into thin rounds, about 1/2cm thick. Place the potato slices in a large pot of salted boiling water and cook for 5 minutes. Drain and set aside.
3. In a large skillet or frying pan, cook the bacon, sliced onions, and garlic.
4. Pour in the white wine and let it simmer for another 2 minutes, allowing the alcohol to evaporate.
5. Layer half of the cooked potato slices in the greased baking dish, forming an even layer. Sprinkle with salt and pepper to taste. Then, distribute half of the bacon and onion mixture over the potatoes.
6. Place half of the Reblochon cheese slices on top of the bacon and onion layer.
7. Repeat the layering process with the remaining potatoes, bacon, onion, and Reblochon cheese.
8. Pour the heavy cream evenly over the top of the tartiflette, allowing it to seep into the layers.
9. Dot the surface with small pieces of butter, which will help give the dish a golden crust during baking.
10. Cover the baking dish with aluminum foil and place it in the preheated oven. Bake for 30 minutes.
11. After 30 minutes, remove the foil and continue baking for another 10-15 minutes, or until the tartiflette turns golden brown and bubbly.
12. Once baked, remove the tartiflette from the oven and let it cool for a few minutes. Garnish with freshly chopped parsley.