Wash and cut potatoes into eighths. Cut the carrots lengthways into strips. Peel and cut the onions into eighths. Mix the vegetables in a bowl with oil, salt and pepper.
Sprinkle everything on a baking sheet lined with baking paper. Place the fish fingers in between. Put in the oven. Bake for about 30 minutes. Layer the vegetables in between, turn the fish fingers.
In the meantime, mix the sour cream, mayonnaise, honey and mustard into a dip and season with salt and pepper. Serve the vegetables and fish fingers with the dip.