Step 1 : slide the onion and pan it with slow heat. Let the slices melt with a drop of olive oil. Crumble the legs flesh. Add the duck crumbs to onions. Pan everything together during 2 minutes. Then, put off the fire.
Step 2 : Mash the potatoes with milk and butter. Add salt and pepper. Mix everything up.
Step 3 : In a big dish, put a layer of puree, a layer of confit and an other layer of puree on top. Put the grated cheese on top. Put in the oven for 15 minutes.