In a large bowl, combine the eggs, sugar and oil and mix until well combined. Add the flour, baking powder, fennel seeds, and optional ingredients if desired, and mix well to form a homogenous batter. Set aside at room temperature for 30 minutes.
Heat the pizzelle iron until very hot. Pour 2 tablespoons of batter onto the iron, close it, and return to the heat. Cook until golden brown, about 2 minutes. Repeat until all the batter is used.
You will need a pizzelle iron to make these cookies.