The potato, sliced ??lengthwise into slices, boil, drain the water. Keep warm. Finely chop the bacon and begin to fry over medium heat, stirring occasionally. When it is half ready, add to it chopped shallots and rosemary sprigs, continue to fry bacon until crisp (2-3 minutes) and a willingness to bow. Remove the rosemary. The bacon and stir in mustard, vinegar, salt and pepper. In a bowl put the hot potato, top with bacon and spices, stir gently and serve hot.