Preheat the oven to 350 degrees F/180 degrees C/Gas 4 and brush a 6-hole muffin tin with the butter. Peel the potatoes and use the julienne blade on a mandoline to make thin matchsticks (or slice by hand). Put the lardons, bay leaf, garlic and onions into a large nonstick frying pan and cook until the lardons are golden brown. Add the wine and reduce until only a couple of tablespoons of liquid remain. Remove the bay leaf. Stir in the potato matchsticks and take off the heat; stir in the Reblochon cubes. Divide the potato mix among the 6 holes in the muffin tin and bake until golden brown and bubbling, 15 to 20 minutes. Serve hot.