In a bowl, combine the flour, Bi-Carb Soda, milk, eggs and salt to make a thin batter. Heat the butter in a frying pan over medium-high heat. Pour in approximately 3 tablespoons of batter and swirl the pan quickly, so that the batter is spread as evenly and as thinly as possible. Fry the pancakes on both sides until golden. Set aside.
For the filling, melt butter in a pan and sprinkle in the flour. Cook for one minute. Add the milk, stirring out any lumps, and bring to a simmer. Stirring constantly, add the eggs until smooth then the parmesan and spinach and season with salt, pepper and nutmeg.
Add 1/3 cup of filling down the centre of each crepe and roll into a cigar shape.