Mix flour, salt and baking powder in a bowl until well blended.
Add egg, oil and ice water. Mix with your hands until a ball forms.
Knead dough until smooth.
Preheat oven to 350°. Line a baking sheet with parchment paper.
Divide dough into two balls. Roll into a rectangle about 12" wide. Place a few drops of oil on the dough.
Spread mashed potato mixture across the top of the dough about 1" from the top edge. Roll up jelly roll style.
Cut into 1½" pieces and place on baking sheet.
Bake for 30-35 minutes, or until brown.