Peel sweet potatoes and cut them into cubes of about 2 cm. Halve the sausage lengthwise and cut into slices. Season potatoes with salt. Spread sausage and potatoes on a baking tray lined with baking paper and drizzle with 2 tbsp. oil.
Cook in the preheated oven (electric cooker: 225 °C/ circulating air: 200 °C/ gas: see manufacturer) for approx. 20 minutes.
In the meantime, clean and wash the spring onions and cut them into rings. Wash and halve the tomatoes. For the vinaigrette, whisk vinegar, salt, pepper, mustard and honey. Add 4 tablespoons of oil drop by drop.
Wash basil, shake dry, pluck leaves from the stems and cut into small pieces. Mix the ingredients and serve. Tastes hot or cold.