Prepare browned butter (optional, otherwise just melt butter): Cut butter into small cubes and let it melt in a large saucepan over medium heat. It will first crackle (butter moisture evaporates).
Then when it stops bubbling, butter will gradually take a nice amber color with a nutty smell. Stop before it blackens. Filter using a drainer and let cool.
In a large bowl, mix flour (ideally previously sifted), sugar and salt. Add eggs and stir with a whisk or a fork. Add butter (melted or browned) and mix.
Finally pour the milk very slowly while stirring constantly.
Set aside to rest at room temperature for 1 hour.
Preheat a 23-cm (9-inch) non-stick frying pan over medium heat. When the skillet is hot, brush with butter.
For each crepe, pour about 1 ladle (about 3/4 tablespoons) of batter in the centre. Tilt frying pan to spread batter evenly until it covers the entire bottom of the frying pan.
When the edge peels off easily and begins to brown, flip the crepe. Continue cooking until it brons a bit.
Then set aside in a plate (see advices to keep them warm as you go).