Heat a crepe pan (or an 8-inch nonstick saute pan) over medium heat and coat with some butter, draining off any excess. Add enough batter to thinly cover the bottom of the pan, about 1/4 cup. Cook over medium heat until the batter appears cooked. Remove the crepe from the pan and reserve. Repeat the process until all of the batter has been used.
For the filling and sauce: Bring a medium pot of water to a boil. Prepare an ice water bath. Add the spinach to the boiling water and let sit for 30 to 60 seconds. Immediately move the spinach to the ice water bath, or run cool water over it in a colander to stop the cooking process. Squeeze all of the water out of the spinach. Combine the taleggio and spinach in a food processor and process until smooth. Season with salt and pepper.
Fill a piping bag halfway with the mixture. Place the crepes on a flat surface. Pipe 1 1/2 tablespoons of the spinach and cheese mixture onto the middle of each crepe. Roll up the crepe and reserve. Repeat with the remaining crepes and filling.