Boil the whole potatoes until they are soft, about 45 minutes. While still warm, peel the potatoes and pass them through vegetable mill onto clean pasta board.
Make a well in the center of the potatoes and sprinkle all over with the flour, using all the flour. Place the egg and salt in the center of the well and using a fork, stir into flour and potatoes, just like making normal pasta. Once the egg is mixed in, bring dough together, kneading gently until a ball is formed. Knead gently another 4 minutes until ball is dry to the touch.
Divide the dough into 6 large balls. Roll each ball into 3/4-inch diameter ropes and cut the ropes into 1-inch long pieces. Flick the pieces off of a fork or along the concave side of a cheese grater to score the sides. Drop the dough pieces into the boiling water and cook until they float to the surface, about 1 minute.
Meanwhile, in a medium bowl, combine the ricotta, cocoa, cinnamon, sugar, and a pinch of salt and stir well.
Drain the gnocchi and place them in the bowl with the cocoa mixture. Toss to coat and remove from the bowl. Place in a clean serving bowl with the citrus peel and raisins, drizzle with the melted butter and serve immediately.