Take butter, water, salt, put everything in a metal bowl or saucepan, and put it on fire.
When the mass boils and the oil dissolves, gradually add flour; stir quickly (preferably with a wooden spoon) so that there are no lumps. Then remove from heat.
When the mass has cooled slightly, beat in the eggs one by one, stirring the dough until smooth. Turn on the oven.
Transfer the dough to a pastry bag and place it on a baking sheet in the form of sausages, 10-15 cm long. (If there is no pastry bag, you can do without it. In this case, take the dough with a spoon dipped in water and put it on a baking sheet.) Bake choux pastries at 180 degrees for 20-25 minutes.
Stuff the finished eclair cakes with custard. For these purposes, you can use a confectionery syringe with a special nozzle. (If there is no such device, cut the side of the cake and fill it with cream.)
Eclair cakes with custard are ready. Enjoy your meal!