In a medium bowl, add 1½ cups of flour and mashed potatoes. Stir to mix. Add sugar, very warm milk, vanilla extract, a pinch of salt, and yeast. Stir a little and then add orange zest and juice. Use a fork to mix vigorously until the dough becomes elastic and soft (about 5 minutes). You may need to add more flour or milk to ensure the right consistency. You should be able to scoop up the dough and it drop from the spoon, keeping a rough shape.
Cover the bowl with a cotton cloth and let rise for about 30 minutes. It will almost double in size.
In a medium-sized bowl, add the sugar and cinnamon. Stir to combine. Set aside.
In a small heavy-bottom pot, add enough oil to a depth of about 2 inches. Set on medium-high heat. It should take about 5 minutes to heat up. Do not leave oil unattended. To test the temperature, dip a fork into the batter and then in the oil. It should start simmering within a second or two. If the temperature is right, then dip one tablespoon in the hot oil to coat. Then, scoop up some batter. Using a second spoon, help ease the batter off the first spoon, sliding it gently into the hot oil. Add enough portions for the size of your pot but do not overcrowd. Simmer for about 3 to 4 minutes, then turn them so that they become golden on all slides. Cook another few minutes. Remove with a sieve and drain on absorbent paper to remove excess oil. (If the dough turns too dark too fast, the inside will be raw. Reduce heat because it is too hot. If the dough sinks and does not start to sizzle within a second, then the oil to not hot enough. Increase heat.)
When still hot, place the fried portions into the bowl with sugar and cinnamon. Toss to coat. Serve immediately.