Preheat the oven to 200°C.
Peel and chop your potatoes. Tip them into a large pan of cold salted water, bring to the boil and cook for 10 minutes until totally soft. Drain and set aside to steam.
Meanwhile, peel and quarter the onions and roughly slice the courgettes.
Tip the potatoes onto your largest baking sheet. Add the onions, courgette and sausages, drizzle everything with olive oil and season with salt and pepper. Roast in the oven for 30 – 40 minutes,
Meanwhile, tip the peas into a bowl and cover with boiling water. Drain immediately and rinse in cold water, then return to the bowl. Use a potato masher to roughly crush the peas. Roughly chop the mint and add it to the bowl, along with the juice of half a lemon and a good drizzle of olive oil. Give everything a good mix until well combined.
Alternatively, place the peas, mint, lemon juice and olive oil into a food processor and give it a quick blitz until a nice chunky but combined consistency.
Tip the sausages, potatoes and veg onto a platter. Scatter with the herby peas, drizzle over a little olive oil and some freshly cracked black pepper.