Preheat oven to 180C

Melt the butter and combine with the olive oil.

Brush the inside of a 20cm square baking dish (or equivalent) with the butter/oil mixture.

Slice each potato quite finely across the short part of the potato making sure you keep all the pieces of the potato together in their original shape.

As each potato is sliced, place it into the baking dish vertically. Add the next potato facing a different way so the result when all potatoes are in the dish is a cross hatch pattern.

Push the onion slices between the potato slices throughout the dish and then sprinkle the potato with salt and pepper.

Brush the potatoes with the 3/4’s of remaining butter/oil mixture thorough and cover the dish with foil.

Place in the oven and bake for 30 mins then remove the foil. Continue to bake for another 60 mins. Remove from oven and brush with the remaining butter/oil mixture.

Meanwhile slice the bacon into small pieces or lardons and cook until crispy and drain on a paper towel.

Remove potatoes from the oven and scatter with the cooked bacon and fresh thyme and return to oven for a further 30 mins and then remove from oven.

Season on top with a little more salt and serve hot.