Use the sugar if the choux paste will be used in a sweet application.
Measure and have ready:
Combine in a large saucepan:
Bring the mixture to a full boil over medium heat. Add the flour all at once and stir vigorously with a wooden spoon. The mixture will look rough at first but it will suddenly become smooth, at which point you should stir faster. The butter may ooze out, which is fine. In a few minutes, the paste will become dry and not cling to the spoon or the sides of the pan, and when the spoon is pressed on it lightly, it will leave a smooth imprint. Do not overcook or overstir at this point, or the dough will fail to puff. Transfer the dough to a large bowl or the bowl of a stand mixer and let cool for 5 minutes, stirring occasionally with a spoon or with the paddle attachment.
Add one at a time, beating vigorously after each addition with a wooden spoon, or on low speed with a mixer:
Make sure that the paste is smooth each time before adding the next egg. Continue to beat until the dough is smooth and shiny. The proper consistency has been reached when a small quantity of the dough will stand erect if scooped up on the end of a spoon. The paste can be covered and refrigerated for up to 4 hours; you do not need to bring the paste to room temperature before shaping.