Let cool for five minutes, then add the breadcrumbs and feta. Mix well, then taste for seasoning. Add more salt if necessary—this is your chance to get the seasoning right while the mixture is egg-free.
Crack one egg into the bowl and mix with your hands to incorporate. Squeeze a small ball of the mixture. If it holds together, begin portioning out the remaining mixture into small balls. If it doesn't hold together, add another egg. (Emily: I usually find one egg to be enough.)
Heat oil in a skillet over medium-high heat. Add balls to pan—they should sizzle when they hit the oil—then turn heat down to medium or medium-low. Cook until golden, about 2 minutes. Use a fork to flip the balls to the other side and cook for another 2 minutes or so.
Serve immediately or at room temperature. Serves 3 to 4 as an appetizer.