Feel free to use vegetarian haggis if you prefer, which you can find online. Tatties (mashed potatoes) don’t usually contain spring onions, so omit them if you like.
Cook the haggis in a large pan of boiling water according to packet instructions.
Meanwhile, cook the turnips or swedes and the potatoes in separate saucepans of boiling salted water for 20–25 minutes, or until tender. Drain the veg separately. Return the turnips or swedes to the pan, add half the butter, and mash, keeping chunky. Season to taste. Cover to keep warm.
Melt the remaining butter in the potato pan, add the spring onions and cook for 1–2 minutes, till softened. Add the potatoes, and mash until quite smooth, seasoning to taste. Cover to keep warm.
Remove the cooked haggis, cut open, and place a portion onto each warmed plate. Divide up the neeps & tatties and serve.