By all means feel free to use well peeled white potato - the point of peeling is to remove all traces of the toxic alkaloid solanine. Potatoes provide a good pack of carbohydrate; the point is to consider whether you need those carbohydrates.
The dish can easily be made more paleo-friendly using mashed cauliflower florets to top.
When using any kind of meat, put ingredients which work well for a particular region which eats a lot of that type of meat - my variation here is lightly Greek inspired with aubergine and Feta, although a nod to the Welsh with leek, and Caerphilly cheese could easily be used in place of Feta.
So, to the cooking ...
Toss in a some shredded leek and soften in the fat with the lid on to recirculate the steam.
Break in a couple of pounds of minced lamb and ensure that it is well coloured.
Pour in a can of peeled plum tomatoes and break up a little. You can add some tomato purée here if you want more of a tomato flavour and even some Worcestershire Sauce.
Cube up some aubergine and courgette, and toss into the pan.
Finally, salt to taste and add in a sprinkle of dried oregano and a clove of minced garlic.
Meanwhile make the cauliflower floret mash.
Steam a whole amount of cauliflower, florets removed carefully and excess stalk trimmed. You can keep the outside leaves and stalk for a rough and ready soup or a refined amuse bouche. Steam until just softened.
Place the cauliflower florets into a tall cylindrical vessel and blend down with a hand blended. Take care not to over-blend - we still want some structure, not a fine purée. Add in a generous knob of butter and allow that to melt, folding in with a spatula.
Once the meat has cooked and the almost entirely reduced, spoon the meat into an oven-proof dish.
Using the spatula, carefully place amounts of the cauliflower mash over the top and then spread around to make a smooth topping. In the oven, this topping will go crisp but you can add to that crunchiess with a little gently cracked sea salt.
Cheese is another ingredient which goes well here - if you do not eat cheese, just leave it out. Using a crumbly cheese like Caerphilly or Feta is perfect!
Place the dish into a pre-heated oven at 200C for 20-30 minutes.
Serve out into a wide bowl with some vegetables of your choice.