Lung Hash with Mashed Potato Topping

Tips from the kitchen

• Let the lung hash actually cook down in the pan before you add anything else. It releases a bit of liquid as it warms, and you want most of that to cook off so the filling isn't watery under the potato.
• The lemon zest matters more than you'd think here. It cuts through the slightly metallic edge that offal can have, so don't skip it or you'll notice the difference.
• Add the spinach off the strongest heat and just fold it through. It wilts in seconds and turns into a sad green mush if you let it sit in the hot pan too long.
• Spread the mashed potato gently with the back of a spoon rather than dumping it on. If you press too hard the filling pushes up the sides and the layers blur together.
• You'll know it's ready when the cheese on top has gone golden and you can hear it bubbling slightly at the edges. Twenty minutes is a guide, your oven decides the rest.