Firmly whisk together the eggs, sugar, extract and milk. Sift together the flour & salt, then whisk into the liquid until incorporated into a batter the texture of heavy cream.
If time allows, refrigerate for two hours (NOTE: while this step isn't necessary, your rosettes will be crispier if you let the batter rest for this period).
Heat 2-3" of canola oil in a deep fryer or heavy frying pan, over medium-high heat to between 360 and 365 degrees. Once the oil has reached heat, submerge the rosette iron into the oil to quickly heat it. Pour your batter into a shallow square pan or container (this will make it easier for you to dip the rosettes).
Carefully dip the heated iron into the batter so that the batter covers the bottom and sides of the iron, but does not cover the tops. Dip the batter covered rosette into the pot, completely submerging it in the oil.
Allow the rosettes to fry until golden brown, using a knife edge to scrape off any excess batter formed at the top. While browning, your rosettes may voluntarily fall off the iron. If so, simply fry them on each side for a few seconds until lightly brown, then remove from pan with tongs or a chopstick.
Drain, invert and cool on paper towels.
After the cookies have cooled, you can either store them in an airtight container or freeze them for later use. Immediately before serving, sprinkle with powdered sugar (and cinnamon, if desired).