In a large measuring cup, combine the flour, eggs, sugar, if using, butter and milk. Using an immersion blender, blend until smooth. Alternatively, blend in a regular blender. Refrigerate for at least 60 minutes.

Heat a crêpe pan or small skillet over medium heat. Spray the pan with nonstick cooking spray and wipe it out with a paper towel. Pour 1/2 cup of batter into the middle of the pan, and tilt the pan from side to side to coat the bottom evenly. When the edges of the crêpe begin to brown, after one to two minutes, flip it in the pan, or use your fingers to turn it over. If necessary, first loosen the crêpe around the edge with the tip of a small knife.

Cook for 30 seconds on the second side, transfer the crêpe to a plate, and cover with parchment paper. Repeat with the remaining batter.