Heat the oven to 220°C/430°F. Put the red onion and sausages in a baking tray, drizzle with a little olive oil and season with plenty of salt and pepper. Put in the oven for 20 minutes.
Bring a large pot of salted water to the boil and boil the potatoes for 12-15 minutes until they’re tender. Drain and set aside.
After 20 minutes take the sausages out the oven. Whisk together your honey and mustard and drizzle over the sausages and onions. Return to the oven for another 5 minutes.
Put the potatoes in a large bowl halving any big ones. When the sausages and onion are cooked halve the onion pieces and chop the sausages into bite sized pieces. Add both to the bowl with the potatoes.
Whisk together all of the dressing ingredients adding a splash of water if it's too thick. Add the rocket to the bowl with the rest of the ingredients and pour over the dressing. Toss well and serve.
Notes
Nutrition information is an estimate and will vary depending on the exact ingredients used.