Heat oil in a pan. Sauté squash and onions together for approx. 5 mins, then season. Add apple juice and bring to boil for a brief time.  Put slices of bread on a baking tray (put baking paper beneath) and put some juice on the slices of bread, then brush some mustard on them. Place cheese and squash on top of the bread slices. Bake for approx. 15 mins in the upper half of the preheated oven (200 degrees). Take out the raclette toasties and sprinkle with the green part of the spring onions that were put aside.