Harissa-baked potato skins and crispy lettuce salad

The basis of this recipe is that you’ll be using up skins from potatoes you’ve already cooked and have sitting around. This is either because you’ve used the cooked flesh to make mash or, in one of life’s great mysteries, your kids have eaten the inside of a jacket potato and left the best bit (i.e. the cooked skins!). Either way, don’t throw them away: they bring a great extra crunch to an already fresh and crunchy salad and they turn this into a dish you can get onto the table in less tha