In a large bowl, whisk together flour, mashed potatoes, salt, sugar, butter, yeast, milk powder and vanilla, stirring with a wooden spoon until a shaggy dough forms then knead until elastic and only slightly tacky.
Form into a tight ball then place dough in oiled bowl and cover with a clean dish towel. Let dough rise in a warm spot in your kitchen until doubled in size, about 1 hour.
Line a large baking sheet with parchment. Punch down dough, then turn onto a lightly floured, form the dough into 2 then flatten, make hole in the middle using a mineral watter bottle cap.
Place doughnuts and holes onto baking sheets, cover with dish towel, and about 30 minutes more.
Fried doughnut with hot oil and medium heat, rotate using chopsticks.
Transfer doughnuts to paper towel-lined baking sheet to drain and cool slightly. Dip into chocolate or glaze, then place onto a cooling rack (or you can eat it immediately!).