there's this veil of confusion surrounding hollandaise sauce. this may not be the traditional way but it's the way I've always made it and i like it. my grandmother calls it blender hollandaise.
1- melt 1 stick butter and let cool while you do the rest... (1/4 lb, 1/2 cup) (not sure of the conversion here so double check)
2- separate 3 eggs and put yolks into blender with dash of white pepper (you can use black but the white blends in better so there's no black specks in your finished sauce) and a good dash (1 tablespoon?) lemon juice. i find real lemon juice really does make a difference here (as opposed to bottled).
3- whizzz up the eggs, pepper, lemon until really frothy, a good 2 minutes.
4- then while whizzing... slowly poor in the melted butter. the two will emulsify well.
i use it right away. i'm not sure how this would handle reheating (your problem will be curdling, separating etc)