1. Remove the cream layer inside the oreo cookies, process the cookies to a fine crumb in a food processor.
2. In a small bowl, sift the flour and then add the oreo fine crumbs from #1 and mix. Set aside.
3. In a medium saucepan, add water, milk, salt, butter and sugar. Heat until the butter is melted and the mixture start boiling (remove from the heat just before it boils). Add the flour mix from #2 and mix them to combine evenly using a wooden spoon. The dough will lump and pull away from the saucepan easily.
4. Spoon the dough into a pastry piping bag fitted with a star tip. Add enough oil to a saucepan and heat to about 180°C over medium heat.
5. Squeeze the dough into the hot oil and cut it to release into the oil with scissors. Fry the churros on each side.
6. Transfer them on a paper towel-lined plate to drain, roll in sugar all sides to coat. Repeat this process with the remaining dough.