Pre-heat the oven to 190°C / Gas 5.
Pop the sausages and onions onto an oven tray. Mix the soy sauce with the honey and thyme and pour over the sausages.
Bake in the oven for 15-20 minutes, making sure to turn the sausages every so often in the sticky glaze.
Meanwhile, boil the potatoes just until soft, then drain into a colander. Mash with the butter and a little salt and pepper.