Set up your Q for indirect cooking and preheat for 10 minutes.
Spray the pan lightly with oil. Arrange a layer of potato over the base of the pan, slightly overlapping. Top with one third of the bacon and onion. Repeat this process twice so you have 3 layers in your pan.
In a bowl combine the cream, milk and mustard and mix together. Pour over the potato mixture. Cover the pan with foil.
When your Q is preheated, open the lid and place the pan with the potato bake on the trivet. Turn the burner control knob(s) to the roast/bake setting. Close the lid and bake for 30 minutes then remove the foil and bake for a further 30 minutes.
Top with the cheese and continue baking for another 30 minutes or until the potato is tender.