Preheat oven to 200 C / Gas 6. Grease a medium sized casserole dish.
Place the apple, carrot and onion in the prepared casserole dish. Stir in 1 tablespoon of plain flour, or enough to coat the vegetables. Season with salt and pepper. Cover the vegetables with all of the sausagemeat. Press it down so it is flat, even and without gaps. Sprinkle sage on top.
Boil the potatoes until just soft. Layer them over the sausagemeat. Brush with oil or butter. Season with salt and pepper.
Bake for around 40 minutes, or until the potatoes are browned and the carrots and onions are soft.
Potatoes can be peeled or unpeeled; use enough to cover the top of the sausagemeat. The quantities of ingredients used in this recipe can be halved for a smaller amount of food. This bake is a meal in itself, so side dishes aren’t necessary. But it goes well with fresh vegetables or baked beans.