Preheat the oven to 170C/325F/gas 3.
Place a little oil in the casserole and sauté the onions on a moderate heat until transparent and starting to take on colour.
Add the carrots, stir and continue to sauté for a few minutes. Remove from the heat.
Place a small knob of lard in the frying pan and brown the meat in batches transferring it to the casserole as you go.
Put back on the heat and stir in the flour. Season and pour in the lamb stock. The stock should just cover the meat and vegetables. If it doesn’t add a little water.
Heat until starting to bubble and then cover and place in the oven for half an hour.
Take the casserole out of the oven and transfer the meat to the baking dish or cazuela. Arrange the sliced potatoes over the top of the meat and brush with melted butter.
Cover the hotpot with kitchen foil and return to the oven and, after an hour, put the oven temperature up to 200C/400F/gas 6 and remove the covering.
Bake for a further half an hour until the potatoes are browned and crisp on top.
Serve immediately with vegetables of your choice.
