Cut potatoes in small cube and boil in salted water for 20min. Strain from water.
Add shredded parmesan and milk, mash altogether.
Pre-heat the oven at 210*C, pour olive oil in an oven dish and soak the two side of the skate.
Add the sliced shallot, the crushed garlic, rosemary, thym, tomatoes, olives and capers on top of the skates. Place on the oven for 15-20min.
On the meantime, add butter in a skillet and add the diced spring onion when it frizzles. Cook for 5 min.