Method:

1. Peel the potatoes and cut them only once lengthwise. Boil them from cold salted water until they’re done.
2. Bake the onions with some pepper, salt and brown sugar until caramelized. Add the brown beef stock and allow to reduce to half.
3. Blend the onion mix halfway in the blender. We still want some chunks in there.
4. Drain the water from the potatoes and put them back on low heat for five minutes to allow excess water to evaporate from the potatoes. Shake the casserole regularly to avoid the potatoes to bake.
5. Add butter, nutmeg, pepper and salt and mash the potatoes finely.
6. Add the potato mash to the onion mix and combine using a spatula
7. Optionally, add the grated parmesan