Boil the potatoes until cooked in salted water. Peel the skin off and crush lightly with a fork. Finely chop the parsley. Mix the parsley with the potatoes and olive oil. Season to taste.
Remove the crusts and lightly press the bread, then cut into 1cm cubes. In a frying pan, heat the olive oil on a medium heat and add the diced bread. Move the bread continuously until golden brown.
Use a sieve to thoroughly drain the croutons and remove any excess oil. Place the croutons on to a paper towel and season. Change the paper until there is no more oil and season again.
Remove the skin of the lemon, discard any seeds and keep the segments. Cut the lemon segments into 1cm dice. Melt the butter in a pan and allow it to start to colour slightly (beurre noisette). Add in
the lemon, diced capers and tarragon.
Carefully wash the skate wings in plenty of cold water and pat them dry with paper towels or a clean kitchen cloth. Leave the fish in the fridge until you’re ready to prepare the meal. Lightly flour each side of the skate wings.
Heat a large, heavy-bottomed frying pan with a tablespoon of oil and sear each side until golden brown – the wings will need around 3-4 minutes on each side. Add a spoon of butter and baste the fish until cooked.
Spoon the crushed potatoes on to each plate. Place a skate wing on top. Spoon the Grenobloise sauce over the fish and sprinkle with croutons.